Question

我在从超类访问变量时遇到了一些问题。请参阅以下两个类：

abstract class StaticEndpoint {

    // API Arguments
    protected $arguments;

    // PDO Object
    protected $PDO;

    public function __construct($args) {
        $this->arguments =  $args;
        try {
                $this->PDO = new PDO('mysql:dbname=dbname;host=127.0.0.1','user', 'pass');
                $this->PDO->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->PDO->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
        } catch (PDOException $e) {
                echo 'Connection failed: ' . $e->getMessage();
        }
    }

    public abstract function executeAll();

    public abstract function executeList();

    public abstract function executeOne();

}

class Endpoint extends StaticEndpoint {

    public function __construct($args) {
        parent::__construct($args);
    }

    public function executeAll() {

    }

    public function executeList() {
        global $status,$response;

        $stmt = parent::PDO->prepare("SELECT id,name FROM users");
        $stmt->execute();
        $users = $stmt->fetch(PDO::FETCH_ASSOC);

        $status['code'] = 200;
        $status['message'] = "Success";
        $response = $users;
    }

    public function executeOne() {

    }
}

然而，这不起作用。我收到以下错误Parse error: syntax error, unexpected '->' (T_OBJECT_OPERATOR) in /path/to/file/Endpoint.php on line 19。第19行是$stmt = parent::PDO->prepare("SELECT id,name FROM users");。我尝试将此行换成并使用$stmt = $this->PDO->prepare("SELECT id,name FROM users");，但这会导致以下错误Notice: Undefined property: Endpoint::$PDO in /path/to/file/Endpoint.php on line 19。从超类访问变量的正确方法是什么？

Answer 1

$this->PDO是访问父类的公共/受保护字段的正确语法。该错误消息告诉我，当您收到错误时，可能没有Endpoint正确扩展StaticEndpoint。

无法获得对父变量的正确访问权限

1 个答案: