带有调用过程的PHP rest API[关闭]

我经常创建这样的API:

public function getUserInfo($id) {
    $stmt = $this->conn->prepare("SELECT id, email FROM users WHERE id = ? ");
    $result = array();

    $stmt->bind_param("s", $id);
    $stmt->execute();
    $stmt->bind_result($id, $email);
    $stmt->fetch();

    $result['id'] = $id;
    $result['email'] = $email;

    return $result;
}

然而,我需要使用过程开发API。我的代码不起作用。

public function getUserInfo($id) {
    $stmt = $this->conn->prepare("call getUser( ? )");
    $result = array();

    $stmt->bind_param("s", $id);
    $stmt->execute();
    $stmt->bind_result($id, $email); // error here
    $stmt->fetch();

    $result['id'] = $id;
    $result['email'] = $email;

    return $result;
}

在这种情况下,我需要做什么才能获得id和电子邮件?