Ajax call not working when sending data to another page - php

Question

Here is my code:
<div class="category" id="<?php echo $cat->term_id; ?>"><?php echo $cat->cat_name; ?> </div>
$(".category").click(function(){
var categ = $(this).attr('id');
alert(categ);
ajax({
type:'POST',
url:'http://myweb.com/rel_notes/?page_id=238',
data:'cat='+categ,
success:function(data) {
if(data) {
} else { // DO SOMETHING
}
}
});
});
and the code behind the page which is receiving the posted data (http://myweb.com//rel_notes/?page_id=238) is here:
<?php
if (isset($_POST['cat']))
{
$cat_id = $_POST['cat'];
echo "<script>alert('$cat_id')</script>";
}
else
$cat_id = NULL;
?>
Problem: It didn't get the value in $cat_id. I tried changing $_POST to $_GET but that didn't work too. So kindly help me where am i missing something?

Answer 1

$.ajax({
type:'POST',
data: {cat: categ},
url:'http://myweb.com//rel_notes/?page_id=238',
error: function() {
alert("Data Error");
},
success:function(data) {
if(data) {
} else {
}
}
});

Answer 2

This is not good way dude.
None can make alert on server side.
You are doing alert code on the server side.
Just replace
<?php
if (isset($_POST['cat']))
{
$cat_id = $_POST['cat'];
echo "<script>alert('$cat_id')</script>";
}
else $cat_id = NULL;
?>
by
<?php
if (isset($_POST['cat']))
{
echo $cat_id = $_POST['cat'];
}
else {
echo $cat_id = "";
}
?>
and alert the code like
$(".category").click(function(){
var categ = $(this).attr('id');
alert(categ);
ajax({
type:'POST',
url:'http://myweb.com/rel_notes/?page_id=238',
data:'cat='+categ,
success:function(data) {
if(data != "") {
alert(data);
}else { // DO SOMETHING
}
}
});
});