Add CakeRequest::__isset()

Fixes #2266

lib/Cake/Network/CakeRequest.php

@@ -413,6 +413,17 @@ public function __get($name) {
 		return null;
 	}
 
+/**
+ * Magic isset method allows isset/empty checks
+ * on routing parameters.
+ *
+ * @param string $name The property being accessed.
+ * @return bool Existence
+ */
+	public function __isset($name) {
+		return isset($this->params[$name]);
+	}
+
 /**
  * Check whether or not a Request is a certain type.  Uses the built in detection rules
  * as well as additional rules defined with CakeRequest::addDetector().  Any detector can be called

lib/Cake/Test/Case/Network/CakeRequestTest.php

@@ -682,6 +682,26 @@ public function test__get() {
 		$this->assertIdentical($request->banana, null);
 	}
 
+/**
+ * Test isset()/empty() with overloaded properties.
+ *
+ * @return void
+ */
+	public function test__isset() {
+		$request = new CakeRequest('some/path');
+		$request->params = array(
+			'controller' => 'posts',
+			'action' => 'view',
+			'plugin' => 'blogs',
+			'named' => array()
+		);
+
+		$this->assertTrue(isset($request->controller));
+		$this->assertFalse(isset($request->notthere));
+		$this->assertFalse(empty($request->controller));
+		$this->assertTrue(empty($request->named));
+	}
+
 /**
  * test the array access implementation
  *