PHP实现链式操作的原理

db.php

class db
{
    public function where()
    {
        //code here
    }
    public function order()
    {
        //code here
    }
    public function limit()
    {
        //code here
    }
}

index.php

$db = new db();

$db->where();
$db->order();
$db->limit();

如果要实现链式调用，这要在方法的结束添加return $this即可。

db.php

class db
{
    public function where()
    {
        //code here
        return $this;
    }
    public function order()
    {
        //code here
        return $this;
    }
    public function limit()
    {
        //code here
        return $this;
    }
}

index.php

$db = new db();

$db->where()->order()->limit();