code: public static function decodeProcessingLevel($level)
      {
          $decoded = null;
  
          $map = [
              0 => 'system',
              1 => 'application'
          ];
  
          if (array_key_exists($level, $map)) {
              $decoded = $map[$level];
          }
  
          return $decoded;
      }
docs: Decode error processing level code
  
  @param int|string $level
  @return string|null