Getting ERR_EMPTY_RESPONSE on $.POST

Question

I have a simple social networking site with chat functionality. I have used $.post a lot in multiple pages. The code works well on all pages except message.php

Answer 1

This is good.

var waiting=false;

$(".abc").keyup(function(){

    if(!waiting){
         waiting = true;
         // code
         $.post('bbs.php',{a:a},function(abc){
            $(".showoff").html(abc);
            waiting=false;
         });
    }
 });