類下的會話

Question

你好，我只是堅持語法，任何人都可以幫我下一個代碼？

class User {  
    protected $userID = preg_replace('#[^0-9]#i', '', $_SESSION['user_id']); 
    protected $useremail = preg_replace('#[^A-Za-z0-9@_.-]#i', '', $_SESSION['user']); 
    protected $userPassword = preg_replace('#[^A-Za-z0-9]#i', '', $_SESSION['user_password']); 

    public function CheckUserLogin(){  
    if(!isset($_SESSION['user'])){ 
     header("location: login.php"); 
     exit();  
    } 

    //Try to find user from session data in database 
    $sql = "SELECT * FROM users WHERE id = '$this->userID' AND email = '$this->useremail' AND password = '$this->userPassword' LIMIT 1"; 
    $res = mysql_query($sql) or die(mysql_error()); 
    $userMatch = mysql_numrows($res); 
    if ($userMatch == 0) { 
     header("location: login.php"); 
     exit(); 
    } 
    } 
} 

Answer 1

首先，請注意，聲明屬性時，你不能分配給它，這不是知道在編譯時的值 - 這意味着你不能調用一個函數來初始化屬性。

此代碼：

protected $userID = preg_replace('#[^0-9]#i', '', $_SESSION['user_id']); 

無效。

作爲參考，你可以閱讀Properties頁的手冊（引述相關的句子）：

They are defined by using one of the keywords public , protected , or private , followed by a normal variable declaration.

This declaration may include an initialization, but this initialization must be a constant value -- that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

你應該先申報財產;以及後來（在你的類的constructor，例如），初始化：

class User { 

    protected $userID; 

    public function __construc() { 
     $this->userID = preg_replace('#[^0-9]#i', '', $_SESSION['user_id']); 
    } 
} 

Answer 2

簡而言之：您只能分配常數表達式到類聲明中的屬性（類體內，但外面一個方法）。其他一切（變量，函數調用......）都被限制在代碼塊（主要函數和方法）中。

但是，你的代碼以你展示的方式是非常神奇的，你應該避免在任何情況下。使用構造函數，而不是

class User {  
    protected $userID; 
    protected $useremail; 
    protected $userPassword; 

    public function __construct ($userId, $user, $password) { 
    $this->userID = preg_replace('#[^0-9]#i', '', $userId); 
    $this->useremail = preg_replace('#[^A-Za-z0-9@_.-]#i', '', $user); 
    $this->userPassword = preg_replace('#[^A-Za-z0-9]#i', '', $password); 
    } 

    // .. 
}