php递归求无限分类子id;

$data=array(
array('cat_id'=>2,'cat_name'=>"新鲜蔬菜" ,'parent_id'=>0),
array('cat_id'=>3,'cat_name'=>'二级分类','parent_id'=>2),
array('cat_id'=>5,'cat_name'=>'二级分类-2','parent_id'=>2),
array('cat_id'=>4,'cat_name'=>'三级分类','parent_id'=>3),
array('cat_id'=>6,'cat_name'=>'三级分类-2','parent_id'=>5),
array('cat_id'=>7,'cat_name'=>'四级分类','parent_id'=>6)
);

function find_children_cat($cat_id,$data,&$tem)
{
foreach($data as $val)
{
if($val['parent_id']==$cat_id)
{
array_push($tem,$val['cat_id']);
find_children_cat($val['cat_id'],$data,$tem);
}
}
}
$tem=array();

find_children_cat(5,$data,$tem);

print_r($tem);