PHP not getting $_POST from ajax post - php

Question

I'm trying to post data to the same page.
I can see that the post from the ajax is working correctly but the $_POST in my index.php isn't finding the post after form submission.
<form method="post" id="classic_login" action="">
<input type="text" name="user" placeholder="Username" class="classic_field" id="user_field" />
<input type="text" name="pass" placeholder="Password" class="classic_field" id="pass_field" />
<input type="submit" name="login" value="Login" class="classic_button" id="login_button" />
<input type="submit" name="register" value="Register" class="classic_button" id="register_button" />
</form>
and I've tried both print_r($_POST) and isset both don't change after submission
print_r($_POST);
if(isset($_POST['user']) && isset($_POST['pass']))
echo "works";
printing formdata after a test submission i get: user=testuser&pass=testpass
$("#classic_login").submit(function(event) {
var formdata = $(this).serialize();
event.preventDefault();
$.ajax
({
url: "",
type: 'POST',
data: formdata,
//success: function(response) { alert(response); },
error: function() { alert("fail"); }
});
});

Answer 1

Alternatively, you could use document.URL to make a request on the same page. Then in PHP, include an exit; after the request:
<?php
if($_SERVER['REQUEST_METHOD'] == 'POST') {
echo '<pre>';
print_r($_POST);
exit; // this is important!
}
?>
<form method="post" id="classic_login" action="">
<input type="text" name="user" placeholder="Username" class="classic_field" id="user_field" />
<input type="text" name="pass" placeholder="Password" class="classic_field" id="pass_field" />
<input type="submit" name="login" value="Login" class="classic_button" id="login_button" />
<input type="submit" name="register" value="Register" class="classic_button" id="register_button" />
</form>
<!-- this is no brainer, of course you need to load the library -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script type="text/javascript">
$("#classic_login").submit(function(event) {
var formdata = $(this).serialize();
event.preventDefault();
$.ajax({
url: document.URL, // you can use this
type: 'POST',
data: formdata,
success: function(response) {
alert(response);
}
});
});
</script>
Sample Output