将公共静态函数的返回值分配给私有变量

Question

There are two classes:

class Db {
    public static function getConnection () {
        /*Initialize parameters*/
        $db = new PDO (...);
        return $db;
    }
}

Class Db initializes and returns a PDO object.

Then I want to do following in another class:

class User {
    private $db = Db::getConnection();
    ....
}

Why am I getting an error here:

private $db = Db::getConnection();

Answer 1

Without knowing the error, it's hard to say, but I'd guess is because you can't do that there, try this.

class User {
    private $db = null;

    function __construct(){
        $this->db = Db::getConnection();
    }

    public function getFriends(){
        return $this->db->query('SELECT * FROM friends');
    }
}