Undefined index even with isset

Question

although i used if(isset()) still get

 Notice: Undefined index: user_name in C:\xampp\htdocs\www\jq\182-186 Users online sample application\users.php

here is part of PHP code

if (isset($_POST['user_name']  , $_POST['action']) || isset($_POST['action'])){

    $user_name = $_POST['user_name'];
    $action = $_POST['action'];

EDIT: || isset($_POST['action']) IS needed for part of jquery that checks DATABASE every half second.

jquery

setInterval(function(){
    $.post('users.php', { action : 'list'} , function(data){
        $('#users_online').html(data);
        });


    },500);

so i can't delete it

Answer 1

Your test is saying:

• If:
  • user_name is set
  • AND
  • action is set
• OR
  • action is set

What this means is that so long as action is set, the test will pass, even if user_name is not set, as is clearly the case in your error message.

Just remove that || isset($_POST['action']) bit and it should work fine.

Also, have a +1 for making me realise that all my isset(...) && isset(...) chains that I've ever written are superfluous XD

Answer 2

Whatever you are trying to achieve with this part isset($_POST['user_name'] , $_POST['action']) it will always be ignored if you have isset($_POST['action']). So if only action index is present, this line will be executed $user_name = $_POST['user_name']; and it will search for user_name index, no matter it does not exist.

You might want to have: if(isset($_POST['user_name']) && isset($_POST['action'])) {