Code doesn’t work inside of Code Snippets but no problem in functions.php

Hi there, I tried adding this code and it crashed my site:

add_filter('wpo_wcpdf_tmp_path', function( $tmp_base ) {
    /*
     * This is an example of a path, please check your current server directory structure.
     * It's recommended to have it outside the /public/ directory.
    */
    $tmp_base = '/home/domains/yourdomain.com/woocommerce-invoices/';
    return $tmp_base;
});

I was just following instructions here:
https://docs.wpovernight.com/woocommerce-pdf-invoices-packing-slips/protect-the-attachments-directory-on-nginx/

The code works fine in functions.php. Any idea why?