(PHP 5 >= 5.3.0)
Allows iterating over a RecursiveIterator to generate an ASCII graphic tree.
$it
   [, int $flags = RecursiveTreeIterator::BYPASS_KEY
   [, int $cit_flags = CachingIterator::CATCH_GET_CHILD
   [, int $mode = RecursiveIteratorIterator::SELF_FIRST
  ]]] )$iterator
   [, int $mode = RecursiveIteratorIterator::LEAVES_ONLY
   [, int $flags = 0
  ]] )RecursiveTreeIterator::BYPASS_CURRENTRecursiveTreeIterator::BYPASS_KEYRecursiveTreeIterator::PREFIX_LEFTRecursiveTreeIterator::PREFIX_MID_HAS_NEXTRecursiveTreeIterator::PREFIX_MID_LASTRecursiveTreeIterator::PREFIX_END_HAS_NEXTRecursiveTreeIterator::PREFIX_END_LASTRecursiveTreeIterator::PREFIX_RIGHT