feat(isValid): Adds getter to access isValid attribute (#128)

Author: rashidsp

Diff for: src/Optimizely/Optimizely.php

@@ -729,4 +729,17 @@ public function getFeatureVariableString($featureFlagKey, $variableKey, $userId,
 
         return $variableValue;
     }
+
+    /**
+     * Determine if the instance of the Optimizely client is valid.
+     * An instance can be deemed invalid if it was not initialized
+     * properly due to an invalid datafile being passed in.
+     *
+     * @return True if the Optimizely instance is valid.
+     *         False if the Optimizely instance is not valid.
+     */
+    public function isValid()
+    {
+        return $this->_isValid;
+    }
 }

Diff for: tests/OptimizelyTest.php

@@ -76,6 +76,18 @@ public function setUp()
             ->getMock();
     }
 
+    public function testIsValidForInvalidOptimizelyObject()
+    {
+        $optlyObject = new Optimizely('Random datafile');
+        $this->assertFalse($optlyObject->isValid());
+    }
+
+    public function testIsValidForValidOptimizelyObject()
+    {
+        $optlyObject = new Optimizely($this->datafile);
+        $this->assertTrue($optlyObject->isValid());
+    }
+
     public function testInitValidEventDispatcher()
     {
         $validDispatcher = new ValidEventDispatcher();