Why does this code snippet create a critical error on my site? [closed]

Question

This snippet used to work fine but with the update to PHP 8.0 it now breaks the site when a WC order is switched to this custom status

//Add custom bulk action in dropdown

add_filter( 'bulk_actions-edit-shop_order', 'register_bulk_action_printed' ); 

function register_bulk_action_printed( $bulk_actions ) {

    $bulk_actions['mark_as_printed'] = 'Change status to Printed';  
    return $bulk_actions;
}

//Bulk action handler

add_action( 'admin_action_mark_as_printed', 'bulk_process_status_printed' );

function bulk_process_status_printed() {
    
    if( !isset( $_REQUEST['post'] ) && !is_array( $_REQUEST['post'] ) )
        return;
        
    foreach( $_REQUEST['post'] as $order_id ) {
    
        $order = new WC_Order( $order_id );
        $order_note = 'That\'s what happened by bulk edit:';
        $order->update_status( 'wc-printed', $order_note, true ); 
        
    }
    
    $location = add_query_arg( array(
        'post_type' => 'shop_order',
        'marked_as_printed' => 1, // marked_as_printed=1 is just the $_GET variable for notices
        'changed' => count( $_REQUEST['post'] ), // number of changed orders
        'ids' => join( $_REQUEST['post'], ',' ),
        'post_status' => 'all'
    ), 'edit.php' );

    wp_redirect( admin_url( $location ) );
    exit;

}

/*
 * Notices
 */
add_action('admin_notices', 'custom_order_status_notices_printed');

function custom_order_status_notices_printed() {
 
    global $pagenow, $typenow;
  
    if( $typenow == 'shop_order' 
     && $pagenow == 'edit.php'
     && isset( $_REQUEST['marked_as_printed'] )
     && $_REQUEST['marked_as_printed'] == 1
     && isset( $_REQUEST['changed'] ) ) {
 
        $message = sprintf( _n( 'Order status changed.', '%s order statuses changed.', $_REQUEST['changed'] ), number_format_i18n( $_REQUEST['changed'] ) );
        echo "<div class=\"updated\"><p>{$message}</p></div>";
    
    }
    
}

This is the error that I get:

PHP Fatal error: Uncaught TypeError: join(): Argument #2 ($array) must be of type ?array, string given in /nas/content/live/allstaruhlmann/wp-content/plugins/code-snippets/php/snippet-ops.php(484) : eval()'d code:32\nStack trace:\n#0 /nas/content/live/allstaruhlmann/wp-content/plugins/code-snippets/php/snippet-ops.php(484) : eval()'d code(32): join(Array, ',')\n#1 /nas/content/live/allstaruhlmann/wp-includes/class-wp-hook.php(307): bulk_process_status_printed('')\n#2 /nas/content/live/allstaruhlmann/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array)\n#3 /nas/content/live/allstaruhlmann/wp-includes/plugin.php(476): WP_Hook->do_action(Array)\n#4 /nas/content/live/allstaruhlmann/wp-admin/admin.php(419): do_action('admin_action_ma...')\n#5 /nas/content/live/allstaruhlmann/wp-admin/edit.php(10): require_once('/nas/content/li...')\n#6 {main}\n thrown in /nas/content/live/allstaruhlmann/wp-content/plugins/code-snippets/php/snippet-ops.php(484) : eval()'d code on line 32, referer: https://allstaruhlmann.com/wp-admin/edit.php?post_type=shop_order

Answer 1

On this line in bulk_process_status_printed():

'ids' => join( $_REQUEST['post'], ',' ),

you've got the arguments backwards: it should be join(separator, array):

'ids' => join( ',', $_REQUEST['post'] ),

This is actually a PHP 8 change not WordPress 6

8.0.0 - Passing the separator after the array is no longer supported.

Answer 2

The critical error in WordPress is generally caused by a malfunctioning plugin, script, or code that prevents WordPress from functioning properly.

WordPress is unable to load the rest of the files it needs unless you resolve this issue.