I'm using this plugin https://github.com/posabsolute/jQuery-Validation-Engine for form validation. Sometimes I need some validation for email or username to check if it exists or not. Base on the tutorial in http://www.position-absolute.com/articles/using-form-ajax-validation-with-the-jquery-validation-engine-plugin/ include this script in the language "ajaxEmailPhp": { "url": settings.base_url