Jquery validation using ajax

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 + "home/check_email",
                    // you may want to pass extra data on the ajax call
                    //"extraData": "name=eric",
                    // if you provide an "alertTextOk", it will show as a green prompt when the field validates
                    "alertTextOk": "* silahkan lanjut",
                    "alertText": "* Email sudah terpakai",
                    "alertTextLoad": "* Validasi, Silahkan menunggu"
                },

And this in your custom js


$("#register_form").validationEngine({
        ajaxFormValidation: true,
        onAjaxFormComplete: ajaxValidationCallback,
        onValidationComplete: ajaxValidationCallback,
        onBeforeAjaxFormValidation: beforeCall
});

                function beforeCall(form, options){
			if (console) 
			console.log("Right before the AJAX form validation call");
			return true;
		}

		// Called once the server replies to the ajax form validation request
		function ajaxValidationCallback(status, form, json, options){
			//if (console) 
			console.log(status);

			if (status === true) {
				alert("the form is valid!");
				// uncomment these lines to submit the form to form.action
				// form.validationEngine('detach');
				// form.submit();
				// or you may use AJAX again to submit the data
			}
		}

in view


in php

public function check_email()
    {
        $get = $this->input->get();
        if (!empty($get))
        {
            $this->load->library('core/student_library');
            $check = $this->student_library->get(array('email' => $get['fieldValue']));
            $check = (empty($check)) ? true : false;
        }
        echo json_encode(array($get['fieldId'],$check));
    }

Troubleshoot

Ajax error: 200 parsererror

Fix the output use echo json_encode($array);

How come it doesn't callback and keep on validating

check the output format or check my example