<?php
  $post_id = get_the_id();

   $custom_fields = get_post_meta($post_id);
echo $custom_fields['mmcode'][0] . '<br />';
  echo print_r($custom_fields);
    if (empty($custom_fields)) {
        error_log("No custom fields found for post ID: $post_id");
        return;
    }

    error_log("Custom fields for post ID $post_id:");

    foreach ($custom_fields as $key => $value) {
        // $value is always an array
        if (is_array($value)) {
            foreach ($value as $val) {
                error_log("$key => $val");
            }
        } else {
            error_log("$key => $value");
        }
    }
?>