diff --git a/php/composer.json b/php/composer.json
index 8e77167..2ce3b9c 100644
--- a/php/composer.json
+++ b/php/composer.json
@@ -1,6 +1,6 @@
 {
   "require": {
-    "google/auth": "^1.18",
+    "google/auth": "^1.42.0",
     "guzzlehttp/guzzle": "*",
     "google/apiclient": "^2.15",
     "google/apiclient-services": "~0.300"
diff --git a/php/demo_eventticket.php b/php/demo_eventticket.php
index 923bdb7..e4d5bbe 100644
--- a/php/demo_eventticket.php
+++ b/php/demo_eventticket.php
@@ -83,12 +83,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -851,12 +851,9 @@ public function createJwtExistingObjects(string $issuerId)
       ]
     ];
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -865,7 +862,7 @@ public function createJwtExistingObjects(string $issuerId)
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_flight.php b/php/demo_flight.php
index c592c31..8053d98 100644
--- a/php/demo_flight.php
+++ b/php/demo_flight.php
@@ -87,12 +87,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -836,12 +836,9 @@ public function createJwtExistingObjects(string $issuerId)
       ]
     ];
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -850,7 +847,7 @@ public function createJwtExistingObjects(string $issuerId)
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_generic.php b/php/demo_generic.php
index 90f76f3..d4fb024 100644
--- a/php/demo_generic.php
+++ b/php/demo_generic.php
@@ -79,12 +79,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -749,12 +749,9 @@ public function createJwtExistingObjects(string $issuerId)
       ]
     ];
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -763,7 +760,7 @@ public function createJwtExistingObjects(string $issuerId)
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_giftcard.php b/php/demo_giftcard.php
index 799a042..6403c9d 100644
--- a/php/demo_giftcard.php
+++ b/php/demo_giftcard.php
@@ -84,12 +84,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -801,12 +801,9 @@ public function createJwtExistingObjects(string $issuerId)
       ]
     ];
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -815,7 +812,7 @@ public function createJwtExistingObjects(string $issuerId)
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_loyalty.php b/php/demo_loyalty.php
index aaa3a9a..336640b 100644
--- a/php/demo_loyalty.php
+++ b/php/demo_loyalty.php
@@ -84,12 +84,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -707,12 +707,9 @@ public function createJwtNewObjects(string $issuerId, string $classSuffix, strin
       ])
     ]);
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -728,7 +725,7 @@ public function createJwtNewObjects(string $issuerId, string $classSuffix, strin
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_offer.php b/php/demo_offer.php
index 4ae5aff..02ef45c 100644
--- a/php/demo_offer.php
+++ b/php/demo_offer.php
@@ -84,12 +84,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -690,12 +690,9 @@ public function createJwtNewObjects(string $issuerId, string $classSuffix, strin
       ])
     ]);
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -711,7 +708,7 @@ public function createJwtNewObjects(string $issuerId, string $classSuffix, strin
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );
 
diff --git a/php/demo_transit.php b/php/demo_transit.php
index 47dd1e8..d47edc0 100644
--- a/php/demo_transit.php
+++ b/php/demo_transit.php
@@ -83,12 +83,12 @@ public function auth()
       Walletobjects::WALLET_OBJECT_ISSUER,
       $this->keyFilePath
     );
+    $this->credentials->useJwtAccessWithScope();
 
     // Initialize Google Wallet API service
-    $this->client = new GoogleClient();
+    $this->client = new GoogleClient(['credentials' => $this->credentials]);
     $this->client->setApplicationName('APPLICATION_NAME');
     $this->client->setScopes(Walletobjects::WALLET_OBJECT_ISSUER);
-    $this->client->setAuthConfig($this->keyFilePath);
 
     $this->service = new Walletobjects($this->client);
   }
@@ -860,12 +860,9 @@ public function createJwtExistingObjects(string $issuerId)
       ]
     ];
 
-    // The service account credentials are used to sign the JWT
-    $serviceAccount = json_decode(file_get_contents($this->keyFilePath), true);
-
     // Create the JWT as an array of key/value pairs
     $claims = [
-      'iss' => $serviceAccount['client_email'],
+      'iss' => $this->credentials->getClientName(),
       'aud' => 'google',
       'origins' => ['www.example.com'],
       'typ' => 'savetowallet',
@@ -874,7 +871,7 @@ public function createJwtExistingObjects(string $issuerId)
 
     $token = JWT::encode(
       $claims,
-      $serviceAccount['private_key'],
+      $this->credentials->getPrivateKey(),
       'RS256'
     );