Can you call a PHP defined value inside of a function call?

Question

Please look at the example code below, when I run it, the defined part is nottranslated in the header function call, is there a special way to do the syntax or is this exact method not possible?

<?PHP
session_start();
define('SITE_URL', 'http://testsddf.com');
$_SESSION['user_role'] = 0;


//if a user is not active, redirect to verification/suspended page
if($_SESSION['user_role'] == 0){
    header('Location: SITE_URL');
}

?>

Answer 1

You cannot do something like this :

define('SITE_URL', 'http://testsddf.com');
header('Location: SITE_URL');

A constant is not interpolated, inside of a string : it's not a variable (and you are using single-quote string, so it wouldn't work with a variable either, here)

You have to use string concatenation, in this situation :

define('SITE_URL', 'http://testsddf.com');
header('Location: ' . SITE_URL);

And, just to put a link to the manual as a reference, you can take a look at Variable parsing : there is nothing there about constants -- even if that's unfortunate.

Answer 2

You either need to do...

header('Location: ' . SITE_URL);

...or...

header("Location: SITE_URL");

...as single quotes don't expand variables. (See this page for more info.)