diff --git a/modules/swagger-codegen/src/main/resources/php/APIClient.mustache b/modules/swagger-codegen/src/main/resources/php/APIClient.mustache
index b8b8eff4295..7f14468a38d 100644
--- a/modules/swagger-codegen/src/main/resources/php/APIClient.mustache
+++ b/modules/swagger-codegen/src/main/resources/php/APIClient.mustache
@@ -41,7 +41,7 @@ class APIClient {
    * @param string $host Base url of the API server (optional)
    */
   function __construct($host = null) {
-    if ($host == null) {
+    if ($host === null) {
       $this->host = '{{basePath}}';
     } else {
       $this->host = $host;
@@ -107,10 +107,12 @@ class APIClient {
    * @return string API key with the prefix
    */
   public function getApiKeyWithPrefix($apiKey) {
-    if (Configuration::$apiKeyPrefix[$apiKey]) {
+    if (isset(Configuration::$apiKeyPrefix[$apiKey])) {
       return Configuration::$apiKeyPrefix[$apiKey]." ".Configuration::$apiKey[$apiKey];
-    } else {
+    } else if (isset(Configuration::$apiKey[$apiKey])) {
       return Configuration::$apiKey[$apiKey];
+    } else {
+      return;
     }
   }
 
@@ -368,7 +370,7 @@ class APIClient {
       $instance = new $class();
       foreach ($instance::$swaggerTypes as $property => $type) {
         $original_property_name = $instance::$attributeMap[$property];
-        if (isset($original_property_name)) {
+        if (isset($original_property_name) && isset($data->$original_property_name)) {
           $instance->$property = self::deserialize($data->$original_property_name, $type);
         }
       }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/APIClient.php b/samples/client/petstore/php/SwaggerClient-php/lib/APIClient.php
index 85087520c8f..e6bdbf351f8 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/APIClient.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/APIClient.php
@@ -41,7 +41,7 @@ class APIClient {
    * @param string $host Base url of the API server (optional)
    */
   function __construct($host = null) {
-    if ($host == null) {
+    if ($host === null) {
       $this->host = 'http://petstore.swagger.io/v2';
     } else {
       $this->host = $host;
@@ -107,10 +107,12 @@ class APIClient {
    * @return string API key with the prefix
    */
   public function getApiKeyWithPrefix($apiKey) {
-    if (Configuration::$apiKeyPrefix[$apiKey]) {
+    if (isset(Configuration::$apiKeyPrefix[$apiKey])) {
       return Configuration::$apiKeyPrefix[$apiKey]." ".Configuration::$apiKey[$apiKey];
-    } else {
+    } else if (isset(Configuration::$apiKey[$apiKey])) {
       return Configuration::$apiKey[$apiKey];
+    } else {
+      return;
     }
   }
 
@@ -373,7 +375,7 @@ class APIClient {
       $instance = new $class();
       foreach ($instance::$swaggerTypes as $property => $type) {
         $original_property_name = $instance::$attributeMap[$property];
-        if (isset($original_property_name)) {
+        if (isset($original_property_name) && isset($data->$original_property_name)) {
           $instance->$property = self::deserialize($data->$original_property_name, $type);
         }
       }
diff --git a/samples/client/petstore/php/SwaggerClient-php/tests/PetApiTest.php b/samples/client/petstore/php/SwaggerClient-php/tests/PetApiTest.php
index bf941756fa6..eadae07066c 100644
--- a/samples/client/petstore/php/SwaggerClient-php/tests/PetApiTest.php
+++ b/samples/client/petstore/php/SwaggerClient-php/tests/PetApiTest.php
@@ -23,7 +23,7 @@ class PetApiTest extends \PHPUnit_Framework_TestCase
     $category->id = $new_pet_id; // use the same id as pet
     $category->name = "test php category";
 
-    $new_pet->tags = [$tag];
+    $new_pet->tags = array($tag);
     $new_pet->category = $category;
 
     $pet_api = new SwaggerClient\PetAPI($api_client);
@@ -47,12 +47,14 @@ class PetApiTest extends \PHPUnit_Framework_TestCase
     # test addDefaultHeader and getDefaultHeader
     SwaggerClient\APIClient::addDefaultHeader('test1', 'value1');
     SwaggerClient\APIClient::addDefaultHeader('test2', 200);
-    $this->assertSame('value1', SwaggerClient\APIClient::getDefaultHeader()['test1']);
-    $this->assertSame(200, SwaggerClient\APIClient::getDefaultHeader()['test2']);
+    $defaultHeader = SwaggerClient\APIClient::getDefaultHeader();
+    $this->assertSame('value1', $defaultHeader['test1']);
+    $this->assertSame(200, $defaultHeader['test2']);
 
     # test deleteDefaultHeader
     SwaggerClient\APIClient::deleteDefaultHeader('test2');
-    $this->assertFalse(isset(SwaggerClient\APIClient::getDefaultHeader()['test2']));
+    $defaultHeader = SwaggerClient\APIClient::getDefaultHeader();
+    $this->assertFalse(isset($defaultHeader['test2']));
 
   }