diff --git a/.circleci/config.yml b/.circleci/config.yml
index 436385e..7497dd5 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -9,6 +9,9 @@ workflows:
       - linux-test:
           name: PHP 7.4
           docker-image: cimg/php:7.4
+      - linux-test:
+          name: PHP 8.0
+          docker-image: cimg/php:8.0
 
 jobs:
   linux-test:
diff --git a/php-server-sdk-shared-tests/.circleci/config.yml b/php-server-sdk-shared-tests/.circleci/config.yml
index fbf729f..90e20f1 100644
--- a/php-server-sdk-shared-tests/.circleci/config.yml
+++ b/php-server-sdk-shared-tests/.circleci/config.yml
@@ -9,6 +9,9 @@ workflows:
       - linux-test:
           name: PHP 7.4
           docker-image: cimg/php:7.4
+      - linux-test:
+          name: PHP 8.0
+          docker-image: cimg/php:8.0
 
 jobs:
   linux-test:
diff --git a/php-server-sdk-shared-tests/composer.json b/php-server-sdk-shared-tests/composer.json
index 62f1e2a..3ed3093 100644
--- a/php-server-sdk-shared-tests/composer.json
+++ b/php-server-sdk-shared-tests/composer.json
@@ -1,4 +1,10 @@
 {
+    "repositories": [
+        {
+            "type": "git",
+            "url": "https://github.com/launchdarkly/php-server-sdk-private.git"
+        }
+    ],
     "name": "launchdarkly/server-sdk-shared-tests",
     "description": "Shared unit test code for LaunchDarkly PHP SDK",
     "license": "Apache-2.0",
@@ -12,7 +18,7 @@
         "php": ">=7.3"
     },
     "require-dev": {
-        "launchdarkly/server-sdk": ">=3.9",
+        "launchdarkly/server-sdk": "4.0.x-dev",
         "phpunit/phpunit": "^9"
     },
     "autoload": {
diff --git a/php-server-sdk-shared-tests/src/DatabaseFeatureRequesterTestBase.php b/php-server-sdk-shared-tests/src/DatabaseFeatureRequesterTestBase.php
index 0c82c47..bb3a65f 100644
--- a/php-server-sdk-shared-tests/src/DatabaseFeatureRequesterTestBase.php
+++ b/php-server-sdk-shared-tests/src/DatabaseFeatureRequesterTestBase.php
@@ -2,15 +2,15 @@
 
 namespace LaunchDarkly\SharedTest;
 
-use LaunchDarkly\FeatureFlag;
 use LaunchDarkly\FeatureRequester;
-use LaunchDarkly\Segment;
+use LaunchDarkly\Impl\Model\FeatureFlag;
+use LaunchDarkly\Impl\Model\Segment;
 use PHPUnit\Framework\TestCase;
 
 /**
  * A base class providing standardized PHPUnit tests for database integrations.
  */
-class DatabaseFeatureRequesterTestBase extends \PHPUnit\Framework\TestCase
+class DatabaseFeatureRequesterTestBase extends TestCase
 {
     const TEST_PREFIX = 'testprefix';
 
diff --git a/php-server-sdk-shared-tests/tests/DatabaseFeatureRequesterTestBaseTest.php b/php-server-sdk-shared-tests/tests/DatabaseFeatureRequesterTestBaseTest.php
index a6a111d..96a75ad 100644
--- a/php-server-sdk-shared-tests/tests/DatabaseFeatureRequesterTestBaseTest.php
+++ b/php-server-sdk-shared-tests/tests/DatabaseFeatureRequesterTestBaseTest.php
@@ -2,16 +2,16 @@
 
 namespace LaunchDarkly\SharedTest\Tests;
 
-use LaunchDarkly\FeatureFlag;
 use LaunchDarkly\FeatureRequester;
-use LaunchDarkly\Segment;
+use LaunchDarkly\Impl\Model\FeatureFlag;
+use LaunchDarkly\Impl\Model\Segment;
 use LaunchDarkly\SharedTest\DatabaseFeatureRequesterTestBase;
 
 class FakeDatabase
 {
 	public static $data = [];
 
-	public static function getItem($prefix, $namespace, $key)
+	public static function getItem(string $prefix, string $namespace, string $key): ?array
 	{
 		$dataSet = self::$data[$prefix] ?? null;
 		if ($dataSet) {
@@ -24,7 +24,7 @@ public static function getItem($prefix, $namespace, $key)
 		return null;
 	}
 
-	public static function getAllItems($prefix, $namespace)
+	public static function getAllItems(string $prefix, string $namespace): array
 	{
 		$itemsOut = [];
 		$dataSet = self::$data[$prefix] ?? [];
@@ -35,7 +35,7 @@ public static function getAllItems($prefix, $namespace)
 		return $itemsOut;
 	}
 
-	public static function putSerializedItem($prefix, $namespace, $key, $json)
+	public static function putSerializedItem(string $prefix, string $namespace, string $key, string $json): void
 	{
 		if (!isset(self::$data[$prefix])) {
     		self::$data[$prefix] = [];
@@ -56,7 +56,7 @@ public function __construct($prefix)
 		$this->prefix = $prefix;
 	}
 
-	public function getFeature($key)
+	public function getFeature(string $key): ?FeatureFlag
 	{
 		$json = FakeDatabase::getItem($this->prefix, 'features', $key);
 		if ($json) {
@@ -66,7 +66,7 @@ public function getFeature($key)
 		return null;
 	}
 
-    public function getSegment($key)
+    public function getSegment(string $key): ?Segment
     {
     	$json = FakeDatabase::getItem($this->prefix, 'segments', $key);
 		if ($json) {
@@ -76,7 +76,7 @@ public function getSegment($key)
 		return null;
     }
 
-    public function getAllFeatures()
+    public function getAllFeatures(): array
     {
     	$jsonList = FakeDatabase::getAllItems($this->prefix, 'features');
     	$itemsOut = [];