accessing the jquery function after success call?

 jQuery(function ($) {
     /* fetch elements and stop form event */
     $("form.follow-form").submit(function (e) {
      /* stop event */
      e.preventDefault();
      /* "on request" */
      $(this).find('i').addClass('active');
      /* send ajax request */
      $.post('listen.php', {
       followID: $(this).find('input').val()
      }, function () {
       /* find and hide button, create element */
       $(e.currentTarget)
         .find('button').hide()
         .after('<span class="following"><span></span>Following!</span>');
      });
     });
    });

i want to kn开发者_StackOverflowow what when i process the mysql query in the listen.php file, how deos it get the success message back, and then perform the change after?

UPDATE

PHP code:

<?php
if ( $_POST['action'] == 'follow' ) {
 $json = '';
  if ( $_POST['fid'] == "2" ) {
  $json = array(  array( "id" => 1 , "name" => "luca" ),
                  array( "id" => 2 , "name" => "marco" )
               );
    }
 echo json_encode($json);
}
?>

jQuery code:

$.ajax({
    type: 'POST',
    url: 'listen.php',
    data: 'action=follow&fid=' + 2, //$(this).find('input').val(),
    success: function(data) {
    var obj = $.parseJSON(data);
        for ( var i = 0; i < obj.length; i++ ) {
         alert( obj[i].id + ' ' + obj[i].name )
         }
    },
    complete: function(data) {
        //alert(data.responseText);
    },
    error: function(data) {
        alert(data);
    }
});

it's XMLHTTP Object that is responsible behind the scene.

your php script should output text... so lets say the query works output "YES" if it doesn't output "NO" then use this function in your $.post():

function (data) {
    if(data=="YES"){
        // worked
    }
    else{
        // didn't work
    }
}