why can't we access values on server side in POST request?

Question

I tried to send the request from jquery ajax with contentType as 'text/plain'. I am unable to access the values on the server side. I am accessing the values using $_POST array in php file. Why is this happening.

jQuery AJAX code:

$.ajax({ 
    type: "POST", 
    data: {o_pass:o_pass,n_pass:n_pass}, 
    url: "changepass", 
    success: function(response) { alert(response); } 
});

Server side:

$old_pass = $_POST['o_pass']; 
$new_pass = $_POST['n_pass'];

Answer 1

Because POST requests should have a content type of application/x-www-form-urlencoded or multipart/form-data so that the server knows what it is dealing with.

What is the reason for sending the request as plain text?

Answer 2

You shouldn't have to worry about the content type, when doing a standard post request.

Try changing your url: changepass to changepass.php. You probably have an html or htm file named changepass that your server is processing your post request.