Trying to see if an email is not a duplicate - php

Question

I've tried to verify if an email already exists in the database.
The same system worked perfectly if I tried to verify a username.
I'm using AJAX and PHP.
This is the file that gets the $_POST variables.
<?php
require_once 'Config.php';
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$email = $_POST['email'];
$password = $_POST['password'];
if (!empty($password) and !empty($email)) {
$notEmpty = true;
include 'validate.php';
if($notEmpty == true and validateEmail($email) == true){
$password = md5($password);
$stmt = $link->prepare("INSERT INTO `Users`(`user_password`, `user_email`) VALUES (?,?)");
$stmt->bind_param("ss",$email,$password);
$stmt->execute();
}
}else{
$notEmpty == false;
}
}
?>
and this is the file that verifies the email doesn't exist on the database.
function validateEmail($user_email){
include '../Backend/Config.php';
$sql = "SELECT `user_password`, `user_email` FROM `Users` WHERE `user_email` = ?";
$stmt = $link->prepare($sql);
$stmt->bind_param("s",$user_email);
$stmt->execute();
$result = $stmt->get_result(); // get the mysqli result
$row = $result->fetch_assoc();
if ($result->num_rows > 0) {
echo 1;
return false;
}
else{
// echo json_encode(array('status' => 'OK'));
echo 0;
return true;
}
}
Js code(ajax):
$('#form').submit(function(e) {
//Don't refresh the page
e.preventDefault();
//Collecting data for the server call
post_data = {
'email' : $('input[name=email]').val(),
'password': $('input[name=password]').val()
};
//AJAX server call to signup.php,which calls validate.php
$.ajax({
method: "POST",
url: "../Backend/signup.php",
data: post_data
})
//Server response and setting the input values to ""
.then(function( msg ) {
if(msg == 0){
console.log("Success, user data inserted. Code: " + msg);
}
//Failed
if(msg == 1){
console.log("Inserting failed. Error code:" + msg);
document.getElementById("error").innerHTML = "This email already exists.";
}
$('input[name=email]').val("");
$('input[name=password]').val("");
});
});
It inserts it anyway, what is the problem here?

Answer 1

If you immediately call num_rows() after executing a prepared statement, it will usually return 0 as it has no way to know how many rows are in the result set, since the result set is not saved in memory yet. You must first call store_result() to buffer the results so that the subsequent call to num_rows() will contain the correct results.
This is explained in the "User Notes" section at the bottom of the PHP documentation for num_rows().