i am getting an error of undefined index :username in php file.. what to do?
event to handel when button2 is clicked
  $("#button2").click(function(){
        var username= $("#PM_username_field").val();
        $.post('abc.php',{username: username },function(data){
        $("#error_pm_username").show().load('abc.php');
        });
    });
       <?php
        $username=$_POST['username'];
        echo $username;
       ?>
 
     
    