PHP generates infinite column tree

Column array:

$arr =array (    ' cid ' = 2, ' cname ' = ' news ', ' pid ' = 0),    Array (' cid ' = 4, ' cname ' = ' sports ', ' pid ' = > 0),    Array (' cid ' = 5, ' cname ' = ' entertainment ', ' pid ' = 0),    Array (' cid ' = 7, ' cname ' = ' hot News ', ' pid ' =&G T;2),    Array (' cid ' = 8, ' cname ' = ' niche News ', ' pid ' = 2),    Array (' cid ' = 9, ' cname ' = ' ballad News ', ' pid ' =&G T 8),);

<?php$arr=array (' cid ' = 2, ' cname ' = ' news ', ' pid ' = 0), array (' cid ' = 4, ' cname ' = ' sports ', ' pi d ' + 0), array (' cid ' = 5, ' cname ' = ' entertainment ', ' pid ' = 0), array (' cid ' = 7, ' cname ' = ' hot News ', ' pid ' = &GT;2), Array (' cid ' = 8, ' cname ' = ' niche News ', ' pid ' = 2), array (' cid ' = 9, ' cname ' = ' ballad News ', ' pid ' =&gt ; 8); function Formattree ($array, $pid = 0, $level = 1, $field = Array (' pid ' = ' pid ', ' id ' = ' = ' id ', ' children ' = ')        Children ') {$arr = array ();                foreach ($array as & $v) {if ($v [$field [' pid ']] = = $pid) {$v [' level '] = $level;                $tem = Formattree ($array, $v [$field [' id '], $v [' Level ']+1, $field);                Determine if there are sub-arrays $tem && $v [$field [' children ']] = $tem;            $arr [] = $v;    }} return $arr; } $tree = Formattree ($arr, 0,1, $field = Array (' pid ' = ' pid ', ' id ' = ' cid ', ' children ' = ' children ')); Echo ' < Pre> '; Print_r ($tree);? >