Cleverly use PHP references to achieve unlimited classification and output hierarchical arrays

Data table fields, id, parentid.
Parent category parentid=0, subcategory parentid=parentid.

function getDataTree($rows, $id='id',$pid = 'parentid',$child = 'child',$root=0) { $tree = array(); // Tree
 if( is_array($rows)){
 $array = array();
 foreach ($rows as $key=>$item){
 $array[$item[$id]] =& $rows[$key];
 }
 foreach($rows as $key=>$item){
 $parentId = $item[$pid];
 if($root == $parentId){
 $tree[] =&$rows[$ key];
 }else{
 if(isset($array[$parentId])){
 $parent =&$array[$parentId];
 $parent[$child][]=&$rows[$key] ;
 }
 }
 }
 }
 return $tree;
}