php 致命错误：不在对象上下文中时使用 $this
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Fatal error: Using $this when not in object context in
提问by B.B King
i have this class for connect to mysqldatabase using php/mysqli:
我有这个类用于mysql使用php/连接到数据库mysqli：
class AuthDB {
private $_db;
public function __construct() {
$this->_db = new mysqli(DB_SERVER, DB_USER, DB_PASS, DB_NAME)
or die("Problem connect to db. Error: ". mysqli_error());
}
public function __destruct() {
$this->_db->close();
unset($this->_db);
}
}
now, i have any page for list user :
现在，我有列表用户的任何页面：
require_once 'classes/AuthDB.class.php';
session_start();
$this->_db = new AuthDB(); // error For This LINE
$query = "SELECT Id, user_salt, password, is_active, is_verified FROM Users where email = ?";
$stmt = $this->_db->prepare($query);
//bind parameters
$stmt->bind_param("s", $email);
//execute statements
if ($stmt->execute()) {
//bind result columnts
$stmt->bind_result($id, $salt, $pass, $active, $ver);
//fetch first row of results
$stmt->fetch();
echo $id;
}
now, i see this error:
现在，我看到这个错误：
Fatal error: Using $this when not in object context in LINE 6
How to fix this error?!
如何修复这个错误？！
回答by Tushar
Like the error says, you can't use $thisoutside of the class definition. To use $_dboutside the class definition, first make it publicinstead of private:
就像错误所说的那样，您不能$this在类定义之外使用。要$_db在类定义之外使用，首先使用它public而不是private：
public $_db
public $_db
Then, use this code:
然后，使用此代码：
$authDb = new AuthDb();
$authDb->_db->prepare($query); // rest of code is the same
--
——
You have to understand what $thisactually means. When used inside a class definition, $thisis used to refer to an object of that class. So if you had a function fooinside AuthDB, and you needed to access $_dbfrom within foo, you would use $thisto tell PHP that you want the $_dbfrom the same object that foobelongs to.
你必须明白什么$this是真正的意思。在类定义$this中使用时，用于引用该类的对象。因此，如果您在foo内部有一个函数AuthDB，并且您需要$_db从内部访问foo，您将使用$this告诉 PHP 您想要$_db来自foo属于同一对象的。
You might want to read this StackOverflow question: PHP: self vs $this
你可能想阅读这个 StackOverflow 问题：PHP: self vs $this
