从静态方法访问非静态属性 [英] Access a non-static property from a static method

问题描述

class database{
    protected $db;

    protected function connect(){
        $this->db = new mysqli( /* DB info */ ); // Connecting to a database
    }
}

class example extends database{
    public function __construct(){
        $this->connect();
    }

    public static function doQuery(){
        $query = $this->db->query("theQuery");   // Not working.
        $query = self::$db->query("theQuery");   // Not working.
        $query = parent::$db->query("theQuery"); // Also not working.
    }
}

我想做类似的事情，但我找不到一种可行的方法，该属性必须为静态...

I want to do something like that but I cant find a way that works, The property has to static...

推荐答案

您可以通过实例化新对象($self = new static;)进行访问.示例代码:

You may access by instantiating a new object ($self = new static;). The sample code:

class Database{

    protected $db;

    protected function connect(){
        $this->db = new mysqli( /* DB info */ ); // Connecting to a database
    }
}


class Example extends Database{

    public function __construct(){
        $this->connect();
    }

    public static function doQuery(){

        $self = new static; //OBJECT INSTANTIATION
        $query = $self->db->query("theQuery");   // working.

    }
}

与致电相同 $self = new Example;，但更多地通过编程，如果更改了类名，则不需要更新.

This is the same as calling $self = new Example; but more programmatically, if the class name is ever changed it does not need updating.

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