Allow if parameter exists in SQLFilter

lib/Doctrine/ORM/Query/Filter/SQLFilter.php

@@ -107,6 +107,22 @@ abstract class SQLFilter
         return $this->em->getConnection()->quote($this->parameters[$name]['value'], $this->parameters[$name]['type']);
     }
 
+    /**
+     * Checks if a parameter was set for the filter.
+     *
+     * @param string $name Name of the parameter.
+     *
+     * @return boolean
+     */
+    final public function hasParameter($name)
+    {
+        if (!isset($this->parameters[$name])) {
+            return false;
+        }
+
+        return true;
+    }
+    
     /**
      * Returns as string representation of the SQLFilter parameters (the state).
      *