diff --git a/src/LaunchDarkly/FeatureFlag.php b/src/LaunchDarkly/FeatureFlag.php
index 46123f8a4..32d85fb29 100644
--- a/src/LaunchDarkly/FeatureFlag.php
+++ b/src/LaunchDarkly/FeatureFlag.php
@@ -29,6 +29,8 @@ class FeatureFlag
     protected $_deleted = false;
     /** @var bool */
     protected $_trackEvents = false;
+    /** @var bool */
+    protected $_trackEventsFallthrough = false;
     /** @var int | null */
     protected $_debugEventsUntilDate = null;
     /** @var bool */
@@ -50,6 +52,7 @@ protected function __construct($key,
                                    array $variations,
                                    $deleted,
                                    $trackEvents,
+                                   $trackEventsFallthrough,
                                    $debugEventsUntilDate,
                                    $clientSide)
     {
@@ -65,6 +68,7 @@ protected function __construct($key,
         $this->_variations = $variations;
         $this->_deleted = $deleted;
         $this->_trackEvents = $trackEvents;
+        $this->_trackEventsFallthrough = $trackEventsFallthrough;
         $this->_debugEventsUntilDate = $debugEventsUntilDate;
         $this->_clientSide = $clientSide;
     }
@@ -85,6 +89,7 @@ public static function getDecoder()
                 $v['variations'] ?: [],
                 $v['deleted'],
                 isset($v['trackEvents']) && $v['trackEvents'],
+                isset($v['trackEventsFallthrough']) && $v['trackEventsFallthrough'],
                 isset($v['debugEventsUntilDate']) ? $v['debugEventsUntilDate'] : null,
                 isset($v['clientSide']) && $v['clientSide']
             );
@@ -104,13 +109,13 @@ public function isOn()
     /**
      * @param LDUser $user
      * @param FeatureRequester $featureRequester
-     * @param bool $includeReasonsInEvents
+     * @param Impl\EventFactory $eventFactory
      * @return EvalResult
      */
-    public function evaluate($user, $featureRequester, $includeReasonsInEvents = false)
+    public function evaluate($user, $featureRequester, $eventFactory)
     {
         $prereqEvents = array();
-        $detail = $this->evaluateInternal($user, $featureRequester, $prereqEvents, $includeReasonsInEvents);
+        $detail = $this->evaluateInternal($user, $featureRequester, $prereqEvents, $eventFactory);
         return new EvalResult($detail, $prereqEvents);
     }
 
@@ -118,16 +123,16 @@ public function evaluate($user, $featureRequester, $includeReasonsInEvents = fal
      * @param LDUser $user
      * @param FeatureRequester $featureRequester
      * @param array $events
-     * @param bool $includeReasonsInEvents
+     * @param Impl\EventFactory $eventFactory
      * @return EvaluationDetail
      */
-    private function evaluateInternal($user, $featureRequester, &$events, $includeReasonsInEvents)
+    private function evaluateInternal($user, $featureRequester, &$events, $eventFactory)
     {
         if (!$this->isOn()) {
             return $this->getOffValue(EvaluationReason::off());
         }
 
-        $prereqFailureReason = $this->checkPrerequisites($user, $featureRequester, $events, $includeReasonsInEvents);
+        $prereqFailureReason = $this->checkPrerequisites($user, $featureRequester, $events, $eventFactory);
         if ($prereqFailureReason !== null) {
             return $this->getOffValue($prereqFailureReason);
         }
@@ -158,10 +163,10 @@ private function evaluateInternal($user, $featureRequester, &$events, $includeRe
      * @param LDUser $user
      * @param FeatureRequester $featureRequester
      * @param array $events
-     * @param bool $includeReasonsInEvents
+     * @param Impl\EventFactory $eventFactory
      * @return EvaluationReason|null
      */
-    private function checkPrerequisites($user, $featureRequester, &$events, $includeReasonsInEvents)
+    private function checkPrerequisites($user, $featureRequester, &$events, $eventFactory)
     {
         if ($this->_prerequisites != null) {
             foreach ($this->_prerequisites as $prereq) {
@@ -172,16 +177,12 @@ private function checkPrerequisites($user, $featureRequester, &$events, $include
                     if ($prereqFeatureFlag == null) {
                         $prereqOk = false;
                     } else {
-                        $prereqEvalResult = $prereqFeatureFlag->evaluateInternal($user, $featureRequester, $events, $includeReasonsInEvents);
+                        $prereqEvalResult = $prereqFeatureFlag->evaluateInternal($user, $featureRequester, $events, $eventFactory);
                         $variation = $prereq->getVariation();
                         if (!$prereqFeatureFlag->isOn() || $prereqEvalResult->getVariationIndex() !== $variation) {
                             $prereqOk = false;
                         }
-                        array_push($events, Util::newFeatureRequestEvent($prereq->getKey(), $user,
-                            $prereqEvalResult->getVariationIndex(), $prereqEvalResult->getValue(),
-                            null, $prereqFeatureFlag->getVersion(), $this->_key,
-                            ($includeReasonsInEvents && $prereqEvalResult) ? $prereqEvalResult->getReason() : null
-                        ));
+                        array_push($events, $eventFactory->newEvalEvent($prereqFeatureFlag, $user, $prereqEvalResult, null, $this));
                     }
                 } catch (EvaluationException $e) {
                     $prereqOk = false;
@@ -258,6 +259,14 @@ public function isDeleted()
         return $this->_deleted;
     }
 
+    /**
+     * @return array
+     */
+    public function getRules()
+    {
+        return $this->_rules;
+    }
+    
     /**
      * @return boolean
      */
@@ -266,6 +275,14 @@ public function isTrackEvents()
         return $this->_trackEvents;
     }
 
+    /**
+     * @return boolean
+     */
+    public function isTrackEventsFallthrough()
+    {
+        return $this->_trackEventsFallthrough;
+    }
+
     /**
      * @return int | null
      */
diff --git a/src/LaunchDarkly/Impl/EventFactory.php b/src/LaunchDarkly/Impl/EventFactory.php
new file mode 100644
index 000000000..068ca4e51
--- /dev/null
+++ b/src/LaunchDarkly/Impl/EventFactory.php
@@ -0,0 +1,127 @@
+<?php
+namespace LaunchDarkly\Impl;
+
+use LaunchDarkly\Util;
+
+class EventFactory
+{
+    /** @var boolean */
+    private $_withReasons;
+
+    public function __construct($withReasons)
+    {
+        $this->_withReasons = $withReasons;
+    }
+
+    public function newEvalEvent($flag, $user, $detail, $default, $prereqOfFlag = null)
+    {
+        $addExperimentData = static::isExperiment($flag, $detail->getReason());
+        $e = array(
+            'kind' => 'feature',
+            'creationDate' => Util::currentTimeUnixMillis(),
+            'key' => $flag->getKey(),
+            'user' => $user,
+            'variation' => $detail->getVariationIndex(),
+            'value' => $detail->getValue(),
+            'default' => $default,
+            'version' => $flag->getVersion()
+        );
+        // the following properties are handled separately so we don't waste bandwidth on unused keys
+        if ($addExperimentData || $flag->isTrackEvents()) {
+            $e['trackEvents'] = true;
+        }
+        if ($flag->getDebugEventsUntilDate()) {
+            $e['debugEventsUntilDate'] = $flag->getDebugEventsUntilDate();
+        }
+        if ($prereqOfFlag) {
+            $e['prereqOf'] = $prereqOfFlag->getKey();
+        }
+        if (($addExperimentData || $this->_withReasons) && $detail->getReason()) {
+            $e['reason'] = $detail->getReason()->jsonSerialize();
+        }
+        return $e;
+    }
+
+    public function newDefaultEvent($flag, $user, $detail)
+    {
+        $e = array(
+            'kind' => 'feature',
+            'creationDate' => Util::currentTimeUnixMillis(),
+            'key' => $flag->getKey(),
+            'user' => $user,
+            'value' => $detail->getValue(),
+            'default' => $detail->getValue(),
+            'version' => $flag->getVersion()
+        );
+        // the following properties are handled separately so we don't waste bandwidth on unused keys
+        if ($flag->isTrackEvents()) {
+            $e['trackEvents'] = true;
+        }
+        if ($flag->getDebugEventsUntilDate()) {
+            $e['debugEventsUntilDate'] = $flag->getDebugEventsUntilDate();
+        }
+        if ($this->_withReasons && $detail->getReason()) {
+            $e['reason'] = $detail->getReason()->jsonSerialize();
+        }
+        return $e;
+    }
+
+    public function newUnknownFlagEvent($key, $user, $detail)
+    {
+        $e = array(
+            'kind' => 'feature',
+            'creationDate' => Util::currentTimeUnixMillis(),
+            'key' => $key,
+            'user' => $user,
+            'value' => $detail->getValue(),
+            'default' => $detail->getValue()
+        );
+        // the following properties are handled separately so we don't waste bandwidth on unused keys
+        if ($this->_withReasons && $detail->getReason()) {
+            $e['reason'] = $detail->getReason()->jsonSerialize();
+        }
+        return $e;
+    }
+
+    public function newIdentifyEvent($user)
+    {
+        return array(
+            'kind' => 'identify',
+            'creationDate' => Util::currentTimeUnixMillis(),
+            'key' => strval($user->getKey()),
+            'user' => $user
+        );
+    }
+    
+    public function newCustomEvent($eventName, $user, $data, $metricValue)
+    {
+        $e = array(
+            'kind' => 'custom',
+            'creationDate' => Util::currentTimeUnixMillis(),
+            'key' => $eventName,
+            'user' => $user
+        );
+        if (isset($data)) {
+            $e['data'] = $data;
+        }
+        if (isset($metricValue)) {
+            $e['metricValue'] = $metricValue;
+        }
+        return $e;
+    }
+
+    private static function isExperiment($flag, $reason)
+    {
+        if ($reason) {
+            switch ($reason->getKind()) {
+                case 'RULE_MATCH':
+                    $i = $reason->getRuleIndex();
+                    $rules = $flag->getRules();
+                    return isset($i) && $i >= 0 && $i < count($rules) && $rules[$i]->isTrackEvents();
+                case 'FALLTHROUGH':
+                    return $flag->isTrackEventsFallthrough();
+            }
+        }
+        return false;
+    }
+}
diff --git a/src/LaunchDarkly/Impl/NullEventProcessor.php b/src/LaunchDarkly/Impl/NullEventProcessor.php
new file mode 100644
index 000000000..36e9d7a6d
--- /dev/null
+++ b/src/LaunchDarkly/Impl/NullEventProcessor.php
@@ -0,0 +1,14 @@
+<?php
+namespace LaunchDarkly;
+
+class NullEventProcessor
+{
+    public function enqueue($event)
+    {
+        return true;
+    }
+
+    public function flush()
+    {
+    }
+}
diff --git a/src/LaunchDarkly/LDClient.php b/src/LaunchDarkly/LDClient.php
index e30b0dde7..31b16a5ce 100644
--- a/src/LaunchDarkly/LDClient.php
+++ b/src/LaunchDarkly/LDClient.php
@@ -1,6 +1,8 @@
 <?php
 namespace LaunchDarkly;
 
+use LaunchDarkly\Impl\EventFactory;
+use LaunchDarkly\Impl\NullEventPublisher;
 use LaunchDarkly\Integrations\Guzzle;
 use Monolog\Handler\ErrorLogHandler;
 use Monolog\Logger;
@@ -33,6 +35,10 @@ class LDClient
     protected $_logger;
     /** @var FeatureRequester */
     protected $_featureRequester;
+    /** @var EventFactory */
+    protected $_eventFactoryDefault;
+    /** @var EventFactory */
+    protected $_eventFactoryWithReasons;
 
     /**
      * Creates a new client instance that connects to LaunchDarkly.
@@ -99,7 +105,20 @@ public function __construct($sdkKey, $options = array())
         }
         $this->_logger = $options['logger'];
 
-        $this->_eventProcessor = new EventProcessor($sdkKey, $options);
+        $this->_eventFactoryDefault = new EventFactory(false);
+        $this->_eventFactoryWithReasons = new EventFactory(true);
+
+        if (isset($options['event_processor'])) {
+            $ep = $options['event_processor'];
+            if (is_callable($ep)) {
+                $ep = $ep($sdkKey, $options);
+            }
+            $this->_eventProcessor = $ep;
+        } elseif ($this->_offline || !$this->_send_events) {
+            $this->_eventProcessor = new EventProcessor($sdkKey, $options);
+        } else {
+            $this->_eventProcessor = new EventProcessor($sdkKey, $options);
+        }
 
         $this->_featureRequester = $this->getFeatureRequester($sdkKey, $options);
     }
@@ -141,7 +160,7 @@ private function getFeatureRequester($sdkKey, array $options)
      */
     public function variation($key, $user, $default = false)
     {
-        $detail = $this->variationDetailInternal($key, $user, $default, false);
+        $detail = $this->variationDetailInternal($key, $user, $default, $this->_eventFactoryDefault);
         return $detail->getValue();
     }
 
@@ -159,29 +178,28 @@ public function variation($key, $user, $default = false)
      */
     public function variationDetail($key, $user, $default = false)
     {
-        return $this->variationDetailInternal($key, $user, $default, true);
+        return $this->variationDetailInternal($key, $user, $default, $this->_eventFactoryWithReasons);
     }
 
     /**
      * @param string $key
      * @param LDUser $user
      * @param mixed $default
-     * @param bool $includeReasonsInEvents
+     * @param EventFactory $eventFactory
      */
-    private function variationDetailInternal($key, $user, $default, $includeReasonsInEvents)
+    private function variationDetailInternal($key, $user, $default, $eventFactory)
     {
         $default = $this->_get_default($key, $default);
 
         $errorResult = function ($errorKind) use ($key, $default) {
             return new EvaluationDetail($default, null, EvaluationReason::error($errorKind));
         };
-        $sendEvent = function ($detail, $flag) use ($key, $user, $default, $includeReasonsInEvents) {
-            if ($this->isOffline() || !$this->_send_events) {
-                return;
+        $sendEvent = function ($detail, $flag) use ($key, $user, $default, $eventFactory) {
+            if ($flag) {
+                $event = $eventFactory->newEvalEvent($flag, $user, $detail, $default);
+            } else {
+                $event = $eventFactory->newUnknownFlagEvent($key, $user, $detail);
             }
-            $event = Util::newFeatureRequestEvent($key, $user, $detail->getVariationIndex(), $detail->getValue(),
-                $default, $flag ? $flag->getVersion() : null, null,
-                $includeReasonsInEvents ? $detail->getReason() : null);
             $this->_eventProcessor->enqueue($event);
         };
 
@@ -211,11 +229,9 @@ private function variationDetailInternal($key, $user, $default, $includeReasonsI
                 $this->_logger->warning("Variation called with null user or null user key! Returning default value");
                 return $result;
             }
-            $evalResult = $flag->evaluate($user, $this->_featureRequester, $includeReasonsInEvents);
-            if (!$this->isOffline() && $this->_send_events) {
-                foreach ($evalResult->getPrerequisiteEvents() as $e) {
-                    $this->_eventProcessor->enqueue($e);
-                }
+            $evalResult = $flag->evaluate($user, $this->_featureRequester, $eventFactory);
+            foreach ($evalResult->getPrerequisiteEvents() as $e) {
+                $this->_eventProcessor->enqueue($e);
             }
             $detail = $evalResult->getDetail();
             if ($detail->isDefaultValue()) {
@@ -261,27 +277,18 @@ public function isOffline()
      *
      * @param $eventName string The name of the event
      * @param $user LDUser The user that performed the event
-     * @param $data mixed
+     * @param $data mixed Optional additional information to associate with the event
+     * @param $metricValue number A numeric value used by the LaunchDarkly experimentation feature in
+     *   numeric custom metrics. Can be omitted if this event is used by only non-numeric metrics. This
+     *   field will also be returned as part of the custom event for Data Export.
      */
-    public function track($eventName, $user, $data)
+    public function track($eventName, $user, $data = null, $metricValue = null)
     {
-        if ($this->isOffline()) {
-            return;
-        }
         if (is_null($user) || $user->isKeyBlank()) {
             $this->_logger->warning("Track called with null user or null/empty user key!");
             return;
         }
-
-        $event = array();
-        $event['user'] = $user;
-        $event['kind'] = "custom";
-        $event['creationDate'] = Util::currentTimeUnixMillis();
-        $event['key'] = $eventName;
-        if (isset($data)) {
-            $event['data'] = $data;
-        }
-        $this->_eventProcessor->enqueue($event);
+        $this->_eventProcessor->enqueue($this->_eventFactoryDefault->newCustomEvent($eventName, $user, $data, $metricValue));
     }
 
     /**
@@ -289,20 +296,11 @@ public function track($eventName, $user, $data)
      */
     public function identify($user)
     {
-        if ($this->isOffline()) {
-            return;
-        }
         if (is_null($user) || $user->isKeyBlank()) {
             $this->_logger->warning("Track called with null user or null/empty user key!");
             return;
         }
-
-        $event = array();
-        $event['user'] = $user;
-        $event['kind'] = "identify";
-        $event['creationDate'] = Util::currentTimeUnixMillis();
-        $event['key'] = strval($user->getKey());
-        $this->_eventProcessor->enqueue($event);
+        $this->_eventProcessor->enqueue($this->_eventFactoryDefault->newIdentifyEvent($user));
     }
 
     /** Returns an array mapping Feature Flag keys to their evaluated results for a given user.
@@ -370,7 +368,7 @@ public function allFlagsState($user, $options = array())
             if ($clientOnly && !$flag->isClientSide()) {
                 continue;
             }
-            $result = $flag->evaluate($user, $preloadedRequester);
+            $result = $flag->evaluate($user, $preloadedRequester, $this->_eventFactoryDefault);
             $state->addFlag($flag, $result->getDetail(), $withReasons, $detailsOnlyIfTracked);
         }
         return $state;
diff --git a/src/LaunchDarkly/Rule.php b/src/LaunchDarkly/Rule.php
index 39d1a9622..5b60a24c1 100644
--- a/src/LaunchDarkly/Rule.php
+++ b/src/LaunchDarkly/Rule.php
@@ -8,12 +8,15 @@ class Rule extends VariationOrRollout
     private $_id = null;
     /** @var Clause[] */
     private $_clauses = array();
+    /** @var boolean */
+    private $_trackEvents;
 
-    protected function __construct($variation, $rollout, $id, array $clauses)
+    protected function __construct($variation, $rollout, $id, array $clauses, $trackEvents)
     {
         parent::__construct($variation, $rollout);
         $this->_id = $id;
         $this->_clauses = $clauses;
+        $this->_trackEvents = $trackEvents;
     }
 
     public static function getDecoder()
@@ -23,7 +26,8 @@ public static function getDecoder()
                 isset($v['variation']) ? $v['variation'] : null,
                 isset($v['rollout']) ? call_user_func(Rollout::getDecoder(), $v['rollout']) : null,
                 isset($v['id']) ? $v['id'] : null,
-                array_map(Clause::getDecoder(), $v['clauses']));
+                array_map(Clause::getDecoder(), $v['clauses']),
+                isset($v['trackEvents']) ? $v['trackEvents'] : false);
         };
     }
 
@@ -56,4 +60,12 @@ public function getClauses()
     {
         return $this->_clauses;
     }
+
+    /**
+     * @return boolean
+     */
+    public function isTrackEvents()
+    {
+        return $this->_trackEvents;
+    }
 }
diff --git a/src/LaunchDarkly/Util.php b/src/LaunchDarkly/Util.php
index e9afd00af..b3619decc 100644
--- a/src/LaunchDarkly/Util.php
+++ b/src/LaunchDarkly/Util.php
@@ -7,7 +7,6 @@
 
 class Util
 {
-
     /**
      * @param $dateTime DateTime
      * @return int
@@ -27,34 +26,6 @@ public static function currentTimeUnixMillis()
         return Util::dateTimeToUnixMillis(new DateTime('now', new DateTimeZone("UTC")));
     }
 
-
-    /**
-     * @param $key string
-     * @param $user LDUser
-     * @param $value
-     * @param $default
-     * @param null $version int | null
-     * @param null $prereqOf string | null
-     * @return array
-     */
-    public static function newFeatureRequestEvent($key, $user, $variation, $value, $default, $version = null, $prereqOf = null, $reason = null)
-    {
-        $event = array();
-        $event['user'] = $user;
-        $event['variation'] = $variation;
-        $event['value'] = $value;
-        $event['kind'] = "feature";
-        $event['creationDate'] = Util::currentTimeUnixMillis();
-        $event['key'] = $key;
-        $event['default'] = $default;
-        $event['version'] = $version;
-        $event['prereqOf'] = $prereqOf;
-        if ($reason !== null) {
-            $event['reason'] = $reason->jsonSerialize();
-        }
-        return $event;
-    }
-
     /**
      * @param $status int
      * @return boolean
diff --git a/tests/FeatureFlagTest.php b/tests/FeatureFlagTest.php
index 19c22e324..e6dd3f94d 100644
--- a/tests/FeatureFlagTest.php
+++ b/tests/FeatureFlagTest.php
@@ -4,6 +4,7 @@
 use LaunchDarkly\EvaluationDetail;
 use LaunchDarkly\EvaluationReason;
 use LaunchDarkly\FeatureFlag;
+use LaunchDarkly\Impl\EventFactory;
 use LaunchDarkly\LDUser;
 use LaunchDarkly\LDUserBuilder;
 use LaunchDarkly\Segment;
@@ -189,6 +190,13 @@ class FeatureFlagTest extends \PHPUnit_Framework_TestCase
     \"deleted\": false
   }";
 
+    private static $eventFactory;
+
+    public static function setUpBeforeClass()
+    {
+        static::$eventFactory = new EventFactory(false);
+    }
+
     public function testDecode()
     {
         $this->assertInstanceOf(FeatureFlag::class, FeatureFlag::decode(\GuzzleHttp\json_decode(FeatureFlagTest::$json1, true)));
@@ -259,7 +267,7 @@ public function testFlagReturnsOffVariationIfFlagIsOff()
         );
         $flag = FeatureFlag::decode($flagJson);
 
-        $result = $flag->evaluate(new LDUser('user'), null);
+        $result = $flag->evaluate(new LDUser('user'), null, static::$eventFactory);
         $detail = new EvaluationDetail('off', 1, EvaluationReason::off());
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -282,7 +290,7 @@ public function testFlagReturnsNullIfFlagIsOffAndOffVariationIsUnspecified()
         );
         $flag = FeatureFlag::decode($flagJson);
 
-        $result = $flag->evaluate(new LDUser('user'), null);
+        $result = $flag->evaluate(new LDUser('user'), null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::off());
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -305,7 +313,7 @@ public function testFlagReturnsErrorIfOffVariationIsTooHigh()
         );
         $flag = FeatureFlag::decode($flagJson);
 
-        $result = $flag->evaluate(new LDUser('user'), null);
+        $result = $flag->evaluate(new LDUser('user'), null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -328,7 +336,7 @@ public function testFlagReturnsErrorIfOffVariationIsNegative()
         );
         $flag = FeatureFlag::decode($flagJson);
 
-        $result = $flag->evaluate(new LDUser('user'), null);
+        $result = $flag->evaluate(new LDUser('user'), null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -356,7 +364,7 @@ public function testFlagReturnsOffVariationIfPrerequisiteIsNotFound()
         $user = $ub->build();
         $requester = new MockFeatureRequesterForFeature();
 
-        $result = $flag->evaluate($user, $requester);
+        $result = $flag->evaluate($user, $requester, static::$eventFactory);
         $detail = new EvaluationDetail('off', 1, EvaluationReason::prerequisiteFailed('feature1'));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -401,7 +409,7 @@ public function testFlagReturnsOffVariationAndEventIfPrerequisiteIsOff()
         $requester->key = $flag1->getKey();
         $requester->val = $flag1;
 
-        $result = $flag0->evaluate($user, $requester);
+        $result = $flag0->evaluate($user, $requester, static::$eventFactory);
         $detail = new EvaluationDetail('off', 1, EvaluationReason::prerequisiteFailed('feature1'));
         self::assertEquals($detail, $result->getDetail());
 
@@ -453,7 +461,7 @@ public function testFlagReturnsOffVariationAndEventIfPrerequisiteIsNotMet()
         $requester->key = $flag1->getKey();
         $requester->val = $flag1;
 
-        $result = $flag0->evaluate($user, $requester);
+        $result = $flag0->evaluate($user, $requester, static::$eventFactory);
         $detail = new EvaluationDetail('off', 1, EvaluationReason::prerequisiteFailed('feature1'));
         self::assertEquals($detail, $result->getDetail());
 
@@ -505,7 +513,7 @@ public function testFlagReturnsFallthroughVariationAndEventIfPrerequisiteIsMetAn
         $requester->key = $flag1->getKey();
         $requester->val = $flag1;
 
-        $result = $flag0->evaluate($user, $requester);
+        $result = $flag0->evaluate($user, $requester, static::$eventFactory);
         $detail = new EvaluationDetail('fall', 0, EvaluationReason::fallthrough());
         self::assertEquals($detail, $result->getDetail());
 
@@ -540,7 +548,7 @@ public function testFlagMatchesUserFromTargets()
         $ub = new LDUserBuilder('userkey');
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         $detail = new EvaluationDetail('on', 2, EvaluationReason::targetMatch());
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -551,7 +559,7 @@ public function testFlagMatchesUserFromRules()
         global $defaultUser;
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($defaultUser, array('variation' => 1))));
 
-        $result = $flag->evaluate($defaultUser, null);
+        $result = $flag->evaluate($defaultUser, null, static::$eventFactory);
         $detail = new EvaluationDetail(true, 1, EvaluationReason::ruleMatch(0, RULE_ID));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -562,7 +570,7 @@ public function testFlagReturnsErrorIfRuleVariationIsTooHigh()
         global $defaultUser;
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($defaultUser, array('variation' => 999))));
 
-        $result = $flag->evaluate($defaultUser, null);
+        $result = $flag->evaluate($defaultUser, null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -573,7 +581,7 @@ public function testFlagReturnsErrorIfRuleVariationIsNegative()
         global $defaultUser;
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($defaultUser, array('variation' => -1))));
 
-        $result = $flag->evaluate($defaultUser, null);
+        $result = $flag->evaluate($defaultUser, null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -584,7 +592,7 @@ public function testFlagReturnsErrorIfRuleHasNoVariationOrRollout()
         global $defaultUser;
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($defaultUser, array())));
 
-        $result = $flag->evaluate($defaultUser, null);
+        $result = $flag->evaluate($defaultUser, null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -596,7 +604,7 @@ public function testFlagReturnsErrorIfRuleHasRolloutWithNoVariations()
         $rollout = array('variations' => array());
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($defaultUser, array('rollout' => $rollout))));
 
-        $result = $flag->evaluate($defaultUser, null);
+        $result = $flag->evaluate($defaultUser, null, static::$eventFactory);
         $detail = new EvaluationDetail(null, null, EvaluationReason::error(EvaluationReason::MALFORMED_FLAG_ERROR));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -613,7 +621,7 @@ public function testRolloutCalculationBucketsByUserKeyByDefault()
         );
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($user, array('rollout' => $rollout))));
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         $detail = new EvaluationDetail(true, 1, EvaluationReason::ruleMatch(0, RULE_ID));
         self::assertEquals($detail, $result->getDetail());
     }
@@ -631,7 +639,7 @@ public function testRolloutCalculationCanBucketBySpecificAttribute()
         );
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($user, array('rollout' => $rollout))));
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         $detail = new EvaluationDetail(true, 1, EvaluationReason::ruleMatch(0, RULE_ID));
         self::assertEquals($detail, $result->getDetail());
     }
@@ -648,7 +656,7 @@ public function testRolloutCalculationIncludesSecondaryKey()
         );
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($user, array('rollout' => $rollout))));
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         $detail = new EvaluationDetail(true, 1, EvaluationReason::ruleMatch(0, RULE_ID));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -667,7 +675,7 @@ public function testRolloutCalculationCoercesSecondaryKeyToString()
         );
         $flag = makeBooleanFlagWithRules(array(makeRuleMatchingUser($user, array('rollout' => $rollout))));
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         $detail = new EvaluationDetail(true, 1, EvaluationReason::ruleMatch(0, RULE_ID));
         self::assertEquals($detail, $result->getDetail());
         self::assertEquals(array(), $result->getPrerequisiteEvents());
@@ -681,7 +689,7 @@ public function testClauseCanMatchBuiltInAttribute()
         $ub->name('Bob');
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         self::assertEquals(true, $result->getDetail()->getValue());
     }
 
@@ -693,7 +701,7 @@ public function testClauseCanMatchCustomAttribute()
         $ub->customAttribute('legs', 4);
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         self::assertEquals(true, $result->getDetail()->getValue());
     }
 
@@ -704,7 +712,7 @@ public function testClauseReturnsFalseForMissingAttribute()
         $ub = new LDUserBuilder('userkey');
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         self::assertEquals(false, $result->getDetail()->getValue());
     }
 
@@ -716,7 +724,7 @@ public function testClauseCanBeNegated()
         $ub->name('Bob');
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         self::assertEquals(false, $result->getDetail()->getValue());
     }
 
@@ -728,7 +736,7 @@ public function testClauseWithUnknownOperatorDoesNotMatch()
         $ub->name('Bob');
         $user = $ub->build();
 
-        $result = $flag->evaluate($user, null);
+        $result = $flag->evaluate($user, null, static::$eventFactory);
         self::assertEquals(false, $result->getDetail()->getValue());
     }
 
@@ -752,7 +760,7 @@ public function testSegmentMatchClauseRetrievesSegmentFromStore()
 
         $feature = makeBooleanFlagWithClauses(array(makeSegmentMatchClause('segkey')));
 
-        $result = $feature->evaluate($defaultUser, $requester);
+        $result = $feature->evaluate($defaultUser, $requester, static::$eventFactory);
 
         self::assertTrue($result->getDetail()->getValue());
     }
@@ -764,7 +772,7 @@ public function testSegmentMatchClauseFallsThroughWithNoErrorsIfSegmentNotFound(
         
         $feature = makeBooleanFlagWithClauses(array(makeSegmentMatchClause('segkey')));
 
-        $result = $feature->evaluate($defaultUser, $requester);
+        $result = $feature->evaluate($defaultUser, $requester, static::$eventFactory);
 
         self::assertFalse($result->getDetail()->getValue());
     }
diff --git a/tests/FileDataFeatureRequesterTest.php b/tests/FileDataFeatureRequesterTest.php
index 1e0e51a2b..7cbdef77c 100644
--- a/tests/FileDataFeatureRequesterTest.php
+++ b/tests/FileDataFeatureRequesterTest.php
@@ -32,7 +32,7 @@ public function testShortcutFlagCanBeEvaluated()
         $fr = Files::featureRequester("./tests/filedata/all-properties.json");
         $flag2 = $fr->getFeature("flag2");
         $this->assertEquals("flag2", $flag2->getKey());
-        $result = $flag2->evaluate(new LDUser("user"), null);
+        $result = $flag2->evaluate(new LDUser("user"), null, null);
         $this->assertEquals("value2", $result->getDetail()->getValue());
     }
 }
diff --git a/tests/LDClientTest.php b/tests/LDClientTest.php
index 25921a2cf..15faa024e 100644
--- a/tests/LDClientTest.php
+++ b/tests/LDClientTest.php
@@ -53,14 +53,20 @@ private function makeFlagThatEvaluatesToNull($key)
         return FeatureFlag::decode($flagJson);
     }
 
+    private function makeClient($overrideOptions = array())
+    {
+        $options = array(
+            'feature_requester_class' => MockFeatureRequester::class,
+            'event_processor' => new MockEventProcessor()
+        );
+        return new LDClient("someKey", array_merge($options, $overrideOptions));
+    }
+    
     public function testVariationReturnsFlagValue()
     {
         $flag = $this->makeOffFlagWithValue('feature', 'value');
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $value = $client->variation('feature', new LDUser('userkey'), 'default');
         $this->assertEquals('value', $value);
@@ -70,10 +76,7 @@ public function testVariationDetailReturnsFlagValue()
     {
         $flag = $this->makeOffFlagWithValue('feature', 'value');
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $detail = $client->variationDetail('feature', new LDUser('userkey'), 'default');
         $this->assertEquals('value', $detail->getValue());
@@ -86,10 +89,7 @@ public function testVariationReturnsDefaultIfFlagEvaluatesToNull()
     {
         $flag = $this->makeFlagThatEvaluatesToNull('feature');
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $value = $client->variation('feature', new LDUser('userkey'), 'default');
         $this->assertEquals('default', $value);
@@ -99,10 +99,7 @@ public function testVariationDetailReturnsDefaultIfFlagEvaluatesToNull()
     {
         $flag = $this->makeFlagThatEvaluatesToNull('feature');
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $detail = $client->variationDetail('feature', new LDUser('userkey'), 'default');
         $this->assertEquals('default', $detail->getValue());
@@ -114,10 +111,7 @@ public function testVariationDetailReturnsDefaultIfFlagEvaluatesToNull()
     public function testVariationReturnsDefaultForUnknownFlag()
     {
         MockFeatureRequester::$flags = array();
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $this->assertEquals('argdef', $client->variation('foo', new LDUser('userkey'), 'argdef'));
     }
@@ -125,10 +119,7 @@ public function testVariationReturnsDefaultForUnknownFlag()
     public function testVariationDetailReturnsDefaultForUnknownFlag()
     {
         MockFeatureRequester::$flags = array();
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $detail = $client->variationDetail('foo', new LDUser('userkey'), 'default');
         $this->assertEquals('default', $detail->getValue());
@@ -140,11 +131,7 @@ public function testVariationDetailReturnsDefaultForUnknownFlag()
     public function testVariationReturnsDefaultFromConfigurationForUnknownFlag()
     {
         MockFeatureRequester::$flags = array();
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false,
-            'defaults' => array('foo' => 'fromarray')
-        ));
+        $client = $this->makeClient(array('defaults' => array('foo' => 'fromarray')));
 
         $this->assertEquals('fromarray', $client->variation('foo', new LDUser('userkey'), 'argdef'));
     }
@@ -153,15 +140,12 @@ public function testVariationSendsEvent()
     {
         $flag = $this->makeOffFlagWithValue('flagkey', 'flagvalue');
         MockFeatureRequester::$flags = array('flagkey' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => true
-        ));
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
 
         $user = new LDUser('userkey');
         $client->variation('flagkey', new LDUser('userkey'), 'default');
-        $proc = $this->getPrivateField($client, '_eventProcessor');
-        $queue = $this->getPrivateField($proc, '_queue');
+        $queue = $ep->getEvents();
         $this->assertEquals(1, sizeof($queue));
         $event = $queue[0];
         $this->assertEquals('feature', $event['kind']);
@@ -171,6 +155,7 @@ public function testVariationSendsEvent()
         $this->assertEquals(1, $event['variation']);
         $this->assertEquals($user, $event['user']);
         $this->assertEquals('default', $event['default']);
+        $this->assertFalse(isset($event['trackEvents']));
         $this->assertFalse(isset($event['reason']));
     }
 
@@ -178,15 +163,12 @@ public function testVariationDetailSendsEvent()
     {
         $flag = $this->makeOffFlagWithValue('flagkey', 'flagvalue');
         MockFeatureRequester::$flags = array('flagkey' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => true
-        ));
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
 
         $user = new LDUser('userkey');
         $client->variationDetail('flagkey', $user, 'default');
-        $proc = $this->getPrivateField($client, '_eventProcessor');
-        $queue = $this->getPrivateField($proc, '_queue');
+        $queue = $ep->getEvents();
         $this->assertEquals(1, sizeof($queue));
         $event = $queue[0];
         $this->assertEquals('feature', $event['kind']);
@@ -196,28 +178,115 @@ public function testVariationDetailSendsEvent()
         $this->assertEquals(1, $event['variation']);
         $this->assertEquals($user, $event['user']);
         $this->assertEquals('default', $event['default']);
+        $this->assertFalse(isset($event['trackEvents']));
         $this->assertEquals(array('kind' => 'OFF'), $event['reason']);
     }
 
+    public function testVariationForcesTrackingWhenMatchedRuleHasTrackEventsSet()
+    {
+        $flagJson = array(
+            'key' => 'flagkey',
+            'version' => 100,
+            'deleted' => false,
+            'on' => true,
+            'targets' => array(),
+            'prerequisites' => array(),
+            'rules' => array(
+                array(
+                    'clauses' => array(
+                        array(
+                            'attribute' => 'key',
+                            'op' => 'in',
+                            'values' => array('userkey'),
+                            'negate' => false
+                        )
+                    ),
+                    'id' => 'rule-id',
+                    'variation' => 1,
+                    'trackEvents' => true
+                )
+            ),
+            'offVariation' => 1,
+            'fallthrough' => array('variation' => 0),
+            'variations' => array('fellthrough', 'flagvalue'),
+            'salt' => ''
+        );
+        $flag = FeatureFlag::decode($flagJson);
+
+        MockFeatureRequester::$flags = array('flagkey' => $flag);
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
+
+        $user = new LDUser('userkey');
+        $client->variation('flagkey', new LDUser('userkey'), 'default');
+        $queue = $ep->getEvents();
+        $this->assertEquals(1, sizeof($queue));
+        $event = $queue[0];
+        $this->assertEquals('feature', $event['kind']);
+        $this->assertEquals('flagkey', $event['key']);
+        $this->assertEquals($flag->getVersion(), $event['version']);
+        $this->assertEquals('flagvalue', $event['value']);
+        $this->assertEquals(1, $event['variation']);
+        $this->assertEquals($user, $event['user']);
+        $this->assertEquals('default', $event['default']);
+        $this->assertTrue($event['trackEvents']);
+        $this->assertEquals(array('kind' => 'RULE_MATCH', 'ruleIndex' => 0, 'ruleId' => 'rule-id'), $event['reason']);
+    }
+
+    public function testVariationForcesTrackingForFallthroughWhenTrackEventsFallthroughIsSet()
+    {
+        $flagJson = array(
+            'key' => 'flagkey',
+            'version' => 100,
+            'deleted' => false,
+            'on' => true,
+            'targets' => array(),
+            'prerequisites' => array(),
+            'rules' => array(),
+            'offVariation' => 1,
+            'fallthrough' => array('variation' => 0),
+            'variations' => array('fellthrough', 'flagvalue'),
+            'salt' => '',
+            'trackEventsFallthrough' => true
+        );
+        $flag = FeatureFlag::decode($flagJson);
+
+        MockFeatureRequester::$flags = array('flagkey' => $flag);
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
+
+        $user = new LDUser('userkey');
+        $client->variation('flagkey', new LDUser('userkey'), 'default');
+        $queue = $ep->getEvents();
+        $this->assertEquals(1, sizeof($queue));
+        $event = $queue[0];
+        $this->assertEquals('feature', $event['kind']);
+        $this->assertEquals('flagkey', $event['key']);
+        $this->assertEquals($flag->getVersion(), $event['version']);
+        $this->assertEquals('fellthrough', $event['value']);
+        $this->assertEquals(0, $event['variation']);
+        $this->assertEquals($user, $event['user']);
+        $this->assertEquals('default', $event['default']);
+        $this->assertTrue($event['trackEvents']);
+        $this->assertEquals(array('kind' => 'FALLTHROUGH'), $event['reason']);
+    }
+
     public function testVariationSendsEventForUnknownFlag()
     {
         MockFeatureRequester::$flags = array();
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => true
-        ));
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
 
         $user = new LDUser('userkey');
         $client->variation('flagkey', new LDUser('userkey'), 'default');
-        $proc = $this->getPrivateField($client, '_eventProcessor');
-        $queue = $this->getPrivateField($proc, '_queue');
+        $queue = $ep->getEvents();
         $this->assertEquals(1, sizeof($queue));
         $event = $queue[0];
         $this->assertEquals('feature', $event['kind']);
         $this->assertEquals('flagkey', $event['key']);
-        $this->assertNull($event['version']);
+        $this->assertFalse(isset($event['version']));
         $this->assertEquals('default', $event['value']);
-        $this->assertNull($event['variation']);
+        $this->assertFalse(isset($event['variation']));
         $this->assertEquals($user, $event['user']);
         $this->assertEquals('default', $event['default']);
         $this->assertFalse(isset($event['reason']));
@@ -226,22 +295,19 @@ public function testVariationSendsEventForUnknownFlag()
     public function testVariationDetailSendsEventForUnknownFlag()
     {
         MockFeatureRequester::$flags = array();
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => true
-        ));
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
 
         $user = new LDUser('userkey');
         $client->variationDetail('flagkey', new LDUser('userkey'), 'default');
-        $proc = $this->getPrivateField($client, '_eventProcessor');
-        $queue = $this->getPrivateField($proc, '_queue');
+        $queue = $ep->getEvents();
         $this->assertEquals(1, sizeof($queue));
         $event = $queue[0];
         $this->assertEquals('feature', $event['kind']);
         $this->assertEquals('flagkey', $event['key']);
-        $this->assertNull($event['version']);
+        $this->assertFalse(isset($event['version']));
         $this->assertEquals('default', $event['value']);
-        $this->assertNull($event['variation']);
+        $this->assertFalse(isset($event['variation']));
         $this->assertEquals($user, $event['user']);
         $this->assertEquals('default', $event['default']);
         $this->assertEquals(array('kind' => 'ERROR', 'errorKind' => 'FLAG_NOT_FOUND'), $event['reason']);
@@ -265,10 +331,7 @@ public function testAllFlagsReturnsFlagValues()
         $flag = FeatureFlag::decode($flagJson);
 
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $builder = new LDUserBuilder(3);
         $user = $builder->build();
@@ -297,10 +360,7 @@ public function testAllFlagsStateReturnsState()
         $flag = FeatureFlag::decode($flagJson);
 
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $builder = new LDUserBuilder(3);
         $user = $builder->build();
@@ -343,10 +403,7 @@ public function testAllFlagsStateReturnsStateWithReasons()
         $flag = FeatureFlag::decode($flagJson);
 
         MockFeatureRequester::$flags = array('feature' => $flag);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $builder = new LDUserBuilder(3);
         $user = $builder->build();
@@ -388,10 +445,7 @@ public function testAllFlagsStateCanFilterForClientSideFlags()
         MockFeatureRequester::$flags = array(
             $flag1->getKey() => $flag1, $flag2->getKey() => $flag2, $flag3->getKey() => $flag3, $flag4->getKey() => $flag4
         );
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $builder = new LDUserBuilder(3);
         $user = $builder->build();
@@ -451,10 +505,7 @@ public function testAllFlagsStateCanOmitDetailsForUntrackedFlags()
         $flag3 = FeatureFlag::decode($flag3Json);
 
         MockFeatureRequester::$flags = array('flag1' => $flag1, 'flag2' => $flag2, 'flag3' => $flag3);
-        $client = new LDClient("someKey", array(
-            'feature_requester_class' => MockFeatureRequester::class,
-            'events' => false
-            ));
+        $client = $this->makeClient();
 
         $builder = new LDUserBuilder(3);
         $user = $builder->build();
@@ -488,6 +539,60 @@ public function testAllFlagsStateCanOmitDetailsForUntrackedFlags()
         $this->assertEquals($expectedState, $state->jsonSerialize());
     }
 
+    public function testTrackSendsEvent()
+    {
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
+
+        $user = new LDUser('userkey');
+        $client->track('eventkey', $user);
+        $queue = $ep->getEvents();
+        $this->assertEquals(1, sizeof($queue));
+        $event = $queue[0];
+        $this->assertEquals('custom', $event['kind']);
+        $this->assertEquals('eventkey', $event['key']);
+        $this->assertEquals($user, $event['user']);
+        $this->assertFalse(isset($event['data']));
+        $this->assertFalse(isset($event['metricValue']));
+    }
+
+    public function testTrackSendsEventWithData()
+    {
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
+        $data = array('thing' => 'stuff');
+
+        $user = new LDUser('userkey');
+        $client->track('eventkey', $user, $data);
+        $queue = $ep->getEvents();
+        $this->assertEquals(1, sizeof($queue));
+        $event = $queue[0];
+        $this->assertEquals('custom', $event['kind']);
+        $this->assertEquals('eventkey', $event['key']);
+        $this->assertEquals($user, $event['user']);
+        $this->assertEquals($data, $event['data']);
+        $this->assertFalse(isset($event['metricValue']));
+    }
+
+    public function testTrackSendsEventWithDataAndMetricValue()
+    {
+        $ep = new MockEventProcessor();
+        $client = $this->makeClient(array('event_processor' => $ep));
+        $data = array('thing' => 'stuff');
+        $metricValue = 1.5;
+
+        $user = new LDUser('userkey');
+        $client->track('eventkey', $user, $data, $metricValue);
+        $queue = $ep->getEvents();
+        $this->assertEquals(1, sizeof($queue));
+        $event = $queue[0];
+        $this->assertEquals('custom', $event['kind']);
+        $this->assertEquals('eventkey', $event['key']);
+        $this->assertEquals($user, $event['user']);
+        $this->assertEquals($data, $event['data']);
+        $this->assertEquals($metricValue, $event['metricValue']);
+    }
+
     public function testOnlyValidFeatureRequester()
     {
         $this->setExpectedException(InvalidArgumentException::class);
diff --git a/tests/MockEventProcessor.php b/tests/MockEventProcessor.php
new file mode 100644
index 000000000..542a4208a
--- /dev/null
+++ b/tests/MockEventProcessor.php
@@ -0,0 +1,27 @@
+<?php
+namespace LaunchDarkly\Tests;
+
+class MockEventProcessor
+{
+    private $_events;
+
+    public function __construct()
+    {
+        $this->_events = array();
+    }
+
+    public function enqueue($event)
+    {
+        $this->_events[] = $event;
+        return true;
+    }
+
+    public function flush()
+    {
+    }
+
+    public function getEvents()
+    {
+        return $this->_events;
+    }
+}