PHP defined not working?

Question

I have a config file that I include early in my program and set this

define('BASE_SLUG','/shop');

I include another file later with these lines

echo BASE_SLUG;
if (defined(BASE_SLUG)) {
  echo ' - yes';
} else {
  echo ' - no';
}

And my output is

/shop - no

how is this possible? BASE_SLUG has the value of /shop and I can echo it, but one line later it says it is not defined

Answer 1

Here is the function prototype for defined

bool defined ( string $name )

You can see that it expects a string value for a constant name. Yours isn't a valid string.

if (defined(BASE_SLUG)) {

Should have the name of constant inside quotes, like :

if (defined('BASE_SLUG')) {

Read this note from PHP Manual

<?php
/* Note the use of quotes, this is important.  This example is checking
 * if the string 'TEST' is the name of a constant named TEST */
if (defined('TEST')) {
    echo TEST;
}
?> 

Source