php递归无限分类原理

$items = array(
array('id' => 1, 'pid' => 0, 'name' => '一级11' ),
array('id' => 11, 'pid' => 0, 'name' => '一级12' ),
array('id' => 2, 'pid' => 1, 'name' => '二级21' ),
array('id' => 10, 'pid' => 11, 'name' => '二级22' ),
array('id' => 3, 'pid' => 1, 'name' => '二级23' ),
array('id' => 12, 'pid' => 11, 'name' => '二级24' ),
array('id' => 13, 'pid' => 12, 'name' => '三级31' ),
array('id' => 9, 'pid' => 1, 'name' => '二级25' ),
);

function formatTree($array, $pid = 0){
$arr = array();
$tem = array();
foreach ($array as $v) {
if ($v['pid'] == $pid) {

$tem = formatTree($array, $v['id']);
//判断是否存在子数组
$tem && ($v['son'] = $tem);
$arr[] = $v;

}

}
return $arr;
}

print_r(formatTree($items,0));