พี่ครับ อยากทราบว่า จะเช็คข้อมูลยังไงอะครับ เมื่อสมัครสมาชิก ในส่วนของ js อะครับ

function singnup_student()
    {
        
         var st = "NAME=" + escape(document.getElementById("name").value) + "&"
         + "Lastname=" + escape(document.getElementById("lastname").value) + "&"
         + "Username=" + escape(document.getElementById("username").value) + "&"
         + "Password=" + escape(document.getElementById("password").value) + "&"
         + "Email=" + escape(document.getElementById("email").value);

         intel.xdk.device.getRemoteData(
             "http://localhost/Ae2DE/singup_ST.php",
             "POST",
             st,
             "success_signup",
             "error_handler");
     }

     function success_signup(data) {
         
         var st = "";
         alert("คุณทำการสมัครสมาชิกเรียบร้อย:"+ data);
          

        
     }

     function error_handler(data) {
         alert("error: " + data);
     }

<?php
$con = mysqli_connect("localhost","root","","ae2de");
if(mysqli_connect_errno($con))
{
		echo "ไม่สามารถทำการเขืช่อมต่อ ฐานข้อมูลได้" . mysqli_connect_errno();
}

mysql_query("SET NAMES UTF8");
		function utf8_urldecode($st)	
		{
			return html_entity_decode(preg_replace("/%u([0-9a-f]{3,4})/i", "&#x\\1;", urldecode($st)), null, '');

		}	

$name= $_POST["NAME"];
$lastname= $_POST["Lastname"];
$username= $_POST["Username"];
$password= $_POST["Password"];
$email= $_POST["Email"];

$name = utf8_urldecode($name);
$lastname = utf8_urldecode($lastname);
$username= utf8_urldecode($username);
$password = utf8_urldecode($password);
$email = utf8_urldecode($email);


//$result = mysqli_query($con,"INSERT INTO `student` VALUES (`$name`, `$lastname`, `$username`, `$password`, `$email`)");
$result = mysqli_query($con,"INSERT INTO student VALUES ('','$name','$lastname','','$username','$password','$email')");

echo "Sign up Complete..** " . $name ;
mysqli_close($con);


?>