protected function keysToString(array $keys) {
    $head = array_shift($keys);
    if ($keys) {
      return $head . '[' . implode('][', $keys) . ']';
    }
    else {
      return $head;
    }
  }
protected function keysToString(array $keys) {
    $head = array_shift($keys);
    if ($keys) {
      return $head . '[' . implode('][', $keys) . ']';
    }
    else {
      return $head;
    }
  }
protected function keysToString ( array $ keys ) { $ head = array_shift ( $ keys ) ; if ( $ keys ) { return $ head . '[' . implode ( '][' , $ keys ) . ']' ; } else { return $ head ; } }
Transforms an key path to a string.

@param string[] $keys
The key path.

@return string
The flattened key path.
Transforms an key path to a string .