PHP基础 -- 链式操作的实现

返回this即可实现链式操作

class db{
    function where(){
        echo ' where ';
        return $this;
    }
    function order(){
        echo ' order ';
        return $this;
    }
    function select(){
        echo ' select ';
    }
}

$db=new db;
$db->where()->order()->select();  // where order select