WP define()

wp-define.php

<?php
namespace Mesoconcepts\WordPress\Config;

/**
 * Warning-free version of PHP's built-in \define() function.
 *
 * @param string $key
 * @param mixed $value
 * @param boolean $case_insensitive
 */
function define($key, $value, $case_insensitive = false) {
    if (!\defined($key)) {
        return \define($key, $value, $case_insensitive);
    }
    else {
        return false;
    }
}