The hostname of your server or local system is an easy way to determine which environment you are working with, either local or production. Prior to PHP 5.3 you would need to utilize the php_uname() function and with 5.3+ there is a built-in function for getting the hostname:

pre-5.3

$hostname = php_uname('n');

5.3+

$hostname = gethostname();

Once you have the hostname, you can do a simple conditional to determine if you are working on running code in your local development environment or out on your server:

if ($hostname == 'production') {
    // Production stuff
} else {
    // Local stuff
}

If you have multiple regions, you could change up the if/else for a switch statement:

switch ($hostname) {
    case 'production':
        // Production stuff
        break;

    case 'staging':
        // Staging stuff
        break;

    case 'development':
    case 'local':
    default:
        // Local stuff
        break;
}

What sort of logic would you need to run on a per environment basis? Well, perhaps you use different database credentials in each environment, or you want to pre-populate the database in your local or staging environments. It’s really up to you and the possibilities are endless!