Check if the input data is already exists in the DB jquery - php

Question

I have a form that adds device name and device id in mysql database. I have written a jquery script that will check whether the device id is already in the db. If exists it will return false. I have the following code-
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script type="text/javascript">
$(document).ready(function(){ //newly added
$('#Submit').click(function() {alert('in');
var checkID = $('#device_id').val(); // assuming this is a input text field
$.post('includes/checkid.php', {'device_id' : checkID}, function(data) {
if(data=='exist') alert("already exists"); return false;
else $('#add_dev').submit();
});
});});
</script>
<form method="post" action="includes/process_add.php" name = "add_dev" id = "add_dev">
<tr><td width="150">Device ID</td><td>:<input type="text" name="device_id" id= "device_id"></td></tr>
<tr><td>Device Name</td><td>:<input type="text" name="device_name"></td></tr>
<tr><td></td><td><br><input type="submit" name="submit" id= "submit" value="Add device"></td></tr>
</form>
and checkid.php is -
<?php
include("connection.php");
$id = $_POST['device_id'];
$sql = mysql_query("SELECT device_id FROM devices WHERE device_id = '$id'");
if (mysql_num_rows($sql) > 0) {
echo "exist";
}else echo 'notexist';
?>
its not working..

Answer 1

Ajax is async, return false outside ajax success callback:
$(document).ready(function () { //newly added
$('#submit').click(function () {
alert('in');
var checkID = $('#device_id').val(); // assuming this is a input text field
$.post('includes/checkid.php', {
'device_id': checkID
}, function (data) {
if (data == 'exist') alert("already exists");
else $('#add_dev').submit();
});
return false;
});
});