AJAX username Availability - php

Question

I have writtin this code to check the email availability.
var email = $('#email_reg').val();
if(email && email.length > 0)
{
if(!isValidEmailAddress(email))
{
isValid = false;
$('#msg_email').html('Email is invalid').show();
}
else
{jQuery.ajax({
type: 'POST',
url: 'check_username.php',
data: 'email='+ email ,
cache: false,
success: function(response){
if(response == 1){
$('#msg_email').html('Email already Exists').show();
isValid=false;
}
else {
$('#msg_email').html('').hide();
}
}
});
}
}
else
{
isValid = false;
$('#msg_email').html('Please enter email').show();
}
The php Code is
<?php
require_once('Connections/connection.php');
$username= mysql_real_escape_string($_REQUEST["email"]);
if (!$con)
{
echo 0;
}
else {
mysql_select_db($database_connection, $connection);
$result = mysql_query("SELECT * FROM vendor_logiin WHERE username='" . $username . "'");
$num = mysql_num_rows($result);
echo $num; //it will always return 1 or 0 since we do not allow multiple users with the same user name.
}
mysql_close();
?>
Now all the others work well like when left it empty and give a wrong email format.But the problem is when i give an email Id that already exists. It didnot give error.
I have no idea what is going wrong.

Answer 1

Since you didn't specify dataType the response is probably treated as text or html and in that case it might be wise to do the comparison as a string:
if (response == "1") {...}
instead of a number. Or use parseInt(response, 10) == 1 if you compare it as a number.