Added dynamic callbacks mode functionality

src/Omnipay/Ecopayz/Message/AbstractRequest.php

@@ -96,6 +96,27 @@ public function setMerchantAccountNumber($value)
         return $this->setParameter('merchantAccountNumber', $value);
     }
 
+    /**
+     * Get the request callback URL.
+     *
+     * @return string
+     */
+    public function getCallbackUrl()
+    {
+        return $this->getParameter('callbackUrl');
+    }
+
+    /**
+     * Sets the request callback URL.
+     *
+     * @param string $value
+     * @return AbstractRequest Provides a fluent interface
+     */
+    public function setCallbackUrl($value)
+    {
+        return $this->setParameter('callbackUrl', $value);
+    }
+
     /**
      * Get calculated checksum
      *

src/Omnipay/Ecopayz/Message/PurchaseRequest.php

@@ -78,6 +78,10 @@ public function getData()
             $data['TransferUrl'] = $notifyUrl;
         }
 
+        if ($callbackUrl = $this->getCallbackUrl()) {
+            $data['CallbackUrl'] = $callbackUrl;
+        }
+
         $data['Checksum'] = $this->calculateArrayChecksum($data);
         return $data;
     }

tests/Omnipay/Ecopayz/Message/PurchaseRequestTest.php

@@ -22,6 +22,7 @@ public function setUp()
             'returnUrl'                 => 'http://example.com/return',
             'cancelUrl'                 => 'http://example.com/cancel',
             'notifyUrl'                 => 'http://example.com/notify',
+            'callbackUrl'               => 'http://example.com/callback',
         ));
     }
 
@@ -36,10 +37,11 @@ public function testGetData()
         $this->assertSame('12.34', $data['Amount']);
         $this->assertSame('EUR', $data['Currency']);
         $this->assertSame('Free Text Description', $data['MerchantFreeText']);
-        $this->assertSame('7320d93a3daa1e296f56fa7f40d6fb8b', $data['Checksum']);
+        $this->assertSame('aa9f664af58922801ac1e23007962af8', $data['Checksum']);
         $this->assertSame('http://example.com/return', $data['OnSuccessUrl']);
         $this->assertSame('http://example.com/cancel', $data['OnFailureUrl']);
         $this->assertSame('http://example.com/notify', $data['TransferUrl']);
+        $this->assertSame('http://example.com/callback', $data['callbackUrl']);
     }
 
     public function testSendData()