How to Use Global Variables Inside Header and Footer

Question

I set global variables for some custom user data in my functions.php to use them in navigation inside header and footer.

if (is_user_logged_in()) {
    # users wordpress id
    global $user_id_wp;
    $user_id_wp = get_current_user_id();
    # users meta page id
    global $user_id_meta;
    $user_id_meta = userMeta(get_current_user_id());
    # users uuid
    global $user_id_uuid;
    $user_id_uuid = get_field("user-uuid", $user_id_meta);
}

Those variables cannot be used inside header.php and footer.php where I need them. Cannot be used means var_dump($user_id_meta) results in NULL, while userMeta($user_id_wp) shows the correct values inside header or footer.

I have tried to set the lines above as function with add_action( 'init', 'globalUserVar' ); but no positive results either. Please help me use my global user vars inside the header and footer. Thanks so much!

Answer 1

In functions.php you can create a constant with the user id, like this.

// if somehow this constant exists this will prevent a php error
if (!defined('CURRENT_USER_ID')) {
    // if user is not logged it this constant will contain 0
    define('CURRENT_USER_ID', get_current_user_id());
}

Now you have a constant variable available anywhere in your theme.

To access it you can simply call it, for example

echo CURRENT_USER_ID;