Note to myself and anybody else using PHP5:

Today I was working on an extension and trying to produce a rootline from a different tree. As this is not possible with standard HMENU objects I had to go the long way and code it myself.

  -2:<?php
  -1: 
   0: $treeGetVars   = t3lib_div::_GET('tx_somesecretextension_tree');
   1: $temp_sys_page = $GLOBALS['TSFE']->sys_page;
   2: $temp_tmpl     = $GLOBALS['TSFE']->tmpl;
   3:         
   4: $rootLine = $temp_sys_page->getRootline($treeGetVars['subpage']);
   5: unset($rootLine[0]);
   6: 
   7: $temp_tmpl->rootLine = array_reverse($rootLine);
   8: 
   9: $menu = t3lib_div::makeInstance('tslib_tmenu');
  10: $menu->parent_cObj = $this->cObj;
  11: $menu->start($temp_tmpl, $temp_sys_page, $this->cObj->data['pages'], $conf, 1);
  12: $menu->makeMenu();
  13: $content = $menu->writeMenu();
  14: 
  15: ?>

So I was trying to be carefull and not modify the global TSFE, instead copying them to a local variable. But right in that moment PHP5 had me! Myself asuming to be working with a local copy I was going nuts and wondering why it was destroying the output of itself and another menu from the same plugin.

The problem:
Have a look at lines 1 and 2! Nothing special, right? Well, remember it's PHP5 and thus it's working with references internally! Instead of working with a copy like I believed I was still working with the actual global instance... So when manipulating my local variable's rootline I was also modifying the global one ... *§$&"!%.

The solution:
Simply force PHP to give you a real copy by using clone:

   1: $temp_sys_page = clone $GLOBALS['TSFE']->sys_page;
   2: $temp_tmpl     = clone $GLOBALS['TSFE']->tmpl;

Have fun with PHP5 - ehm for those TYPO3 5.0 guys out there also PHP6 ;-) - and references!