gistfile1.php

<?php


function treeWalker($fnCallback, $strTable, $intStart=0, $orderBy='pid, sorting')
{
	$arrItemsByPid = array();
	$arrItems = \Database::getInstance()->execute('SELECT * FROM ' . $strTable . ' ORDER BY ' . $orderBy)->fetchAllAssoc();
	$strResult = '';

	foreach($arrItems as $arrItem)
	{
		$arrItemsByPid[$arrItem['pid']][] = $arrItem;
	}

	function iterate($pid, &$arrItemsByPid, &$fnCallback, &$strResult, $level=0)
	{
		for ($i=0, $len=count($arrItemsByPid[$pid]); $i<$len; $i++)
		{
			$arrItem = $arrItemsByPid[$pid][$i];
			$varRes = $fnCallback($arrItem, $level, $i, $i===$len-1);
			if (is_string($varRes))
			{
				$strResult .= $varRes;
			}
			if (isset($arrItemsByPid[$arrItem['id']]))
			{
				iterate($arrItem['id'], $arrItemsByPid, $fnCallback, $strResult, $level+1);
			}
		}
	};

	iterate($intStart, $arrItemsByPid, $fnCallback, $strResult, 0);

	return $strResult;
}