How to define constants safely in Laravel config files

defining-config-constants.md

Doing a simple CONST declaration in config files can cause errors when enabling caching in Laravel. The config file appears to be loaded more than once and the second time causes an error because the constant is already defined.

The safe way to do it is to use the old syntax and only try to define the constant if it has not already been defined, as the following example shows:

<?php

use Illuminate\Support\Facades\Facade;

if (!defined('DEFAULT_PHONE_NO'))
    define('DEFAULT_PHONE_NO', '0123456789');

if (!defined('DEFAULT_EMAIL'))
    define('DEFAULT_EMAIL', 'info@example.com');