fix

DependencyInjection/Configuration.php

@@ -82,6 +82,7 @@ class Configuration implements ConfigurationInterface
                         ->end()
                         ->scalarNode('job_prefix')
                             ->defaultValue(null)
+                        ->end()
                         ->scalarNode('generate-unique-key')
                             ->defaultValue(true)
                         ->end()

Service/GearmanClient.php

@@ -604,10 +604,10 @@ class GearmanClient extends AbstractGearmanService
      *
      * @param string $name
      * @param string $params
-     * @return null|string
+     * @return string
      */
     private function generateUniqueKey($name, $params = '')
     {
-        return md5($name.$params);
+        return md5($name . $params);
     }
 }