How to catch php message return value and show it by java script alert?

How to catch php message return value and show it by java script alert?

i'm using HTML5 form validation and and wana to change custom validation
error to user, but i found a function that works on javascript, my problem
is that my consol give me some tip, it said TypeError:
$(...).setCustomValidity is not a function, i know that it,s java scripts
function, so what should i use in jquery??? is there any same function??
$(document).ready(function() {
//the min chars for username
//when field is focus out
$('#phone').focusout(function(){
//run the character number check
//get the phone
$phone = $('#phone').val();
//use ajax to run the check
$.ajax({
url: 'check.php',
type: 'POST',
dataType: 'html',
data: {
phone : $('#phone').val()
},
success:function(response){
if(response == "1"){
$('#phone').setCustomValidity('blahblahbla ');
}
}
});
});
here is my code, thanks for your answers.