$_GET and WordPress

Question

I want to add a custom php file to a WordPress to do a simple action.

So far I have in my theme index.php file:

<a href="myfile.php?size=md">link</a>

and the php is

<?php echo "hello world"; ?>

<?php echo $_GET["size"]; ?>

<?php echo "hello world"; ?>

The link, once clicked, displays:

hello world

Is WordPress taking over the $_GET function and I need to do some tricks to use it? What am I doing wrong?

Edit:

<?echo "hello world";?>
<? 
  if (array_key_exists('size', $_GET))
    echo $_GET['size'];
?>
<?echo "end";?>

Ouputs :

hello world

Answer 1

See the solution :

In order to be able to add and work with your own custom query vars that you append to URLs, (eg: www.site.com/some_page/?my_var=foo - for example using add_query_arg()) you need to add them to the public query variables available to WP_Query. These are built up when WP_Query instantiates, but fortunately are passed through a filter query_vars before they are actually used to populate the $query_vars property of WP_Query.

For your case :

  function add_query_vars_filter( $vars ){
       $vars[] = "size";
       return $vars;
  }
  add_filter( 'query_vars', 'add_query_vars_filter' );

and on your template page call the get methode like that :

$size_var = (get_query_var('size')) ? get_query_var('size') : false;
if($size_var){
   // etc...
}

More at the Codex : http://codex.wordpress.org/Function_Reference/get_query_var

I hope it helps !

Answer 2

Not sure if this will show anything but try turning on error reporting with:

<?php
   error_reporting(E_ALL);
   ini_set('display_errors', true);
?>

at the top of your page before any other code.

Edit:

From the OP comments:

silly question, but are you sure you are viewing the results of your latest changes to the file and not a cached copy of the page or something? Change "hello world" to something else. (Sorry grasping at straws, but this happened to me before) – Zenshai

ahaha, the person that were doing the changes didn't changed the correct file. It's working now – marcgg

peer programming fail ^^ – marcgg

That would be an "or something", can't tell you how many times i've done something like that. Glad you were able to figure it out in the end. – Zenshai

I usually discover errors like these only when they begin to defy everything I know about a language or an environment.