function get_category($category_id ){
$con = mysqli_connect('127.0.0.1','root','','sdjd') or die('数据库连接失败');
$category_ids = $category_id.",";
$sql_cat = "select id,name,parent_id from category where parent_id = ".$category_id."";
$child_category = mysqli_query($con,$sql_cat);
foreach( $child_category as $key => $val){
// print_r($val);exit;
$category_ids .= get_category( $val["cat_id"] );
}
return $category_ids;
} 