This fn allows you write to the WordPress debug log if you have it enabled in the wp_config file.

WordPress Debug Log | Write to Log

/**
 * Write to Debug Log
 *
 * Add to your functions.php file for use in a theme.
 * Remember to remove from live environment.
 *
 * @param object $log
 * @return void
 */
if (!function_exists('write_log')) {
  function write_log($log) {
    if (is_array($log) || is_object($log)) {
      error_log(print_r($log, true))
    } else {
      error_log($log)
    }
  }
}



// Examples Below

// Use in any php file to see if line ever gets called.
write_log( __LINE__ );
// Or to check if a var is what it's suppose to be.
write_log( $my_post );
// Or to log information.
write_log( "The following post {$my_post} was written by {$author_id}" );