Php 无法在会话类中创建类实例

我试图在数据库中记录会话。我创建了一个类，并试图在其构造中调用数据库类。 我得到这个错误：

警告：缺少SafePDO:：_构造的参数1，在

这是我的数据库类：

Class SafePDO extends PDO {

    public static function exception_handler($exception) {
        // Output the exception details
        die('Uncaught exception: ' . $exception->getMessage());
    }

    public function __construct($dsn, $username = '', $password = '', $driver_options = array()) {

        // Temporarily change the PHP exception handler while we...
        set_exception_handler(array(__CLASS__, 'exception_handler'));

        // ... create a PDO object
        parent::__construct($dsn, $username, $password, $driver_options);

        // Change the exception handler back to whatever it was before
        restore_exception_handler();
    }

}

$db = new PDO('mysql:host=localhost;dbname=mynshost_tarrot;charset=utf8', 'mynshost_tarrot', 'PickTarrot2');
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

这是我的课程：

class Session {


    private $db;

    public function __construct() {
        // Instantiate new Database object

        $this->db = new SafePDO;

// Set handler to overide SESSION
        session_set_save_handler(
                array($this, "_open"), array($this, "_close"), array($this, "_read"), array($this, "_write"), array($this, "_destroy"), array($this, "_gc")
        );

        // Start the session
        session_start();
    }

    /**
     * Open
     */
    public function _open() {
        // If successful
        if ($this->db) {
            return true;
        }
        return false;
    }

    /**
     * Close
     */
    public function _close() {
        // Close the database
        if ($this->db->close()) {
            return true;
        }
        return false;
    }

    /**
     * Read
     */
    public function _read($id) {


        try {
            $stmt = $db->prepare("SELECT data FROM sessions WHERE id = :user_id");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->execute();
            $row_sess_data = $stmt->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }

        return $row_sess_data['data'];
    }

    /**
     * Write
     */
    public function _write($user_id, $data) {
        // Create time stamp
        $access = time();

        try {
            $stmt = $db->prepare("REPLACE INTO sessions VALUES (:user_id, :access, :data)");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->bindValue(':access', $access, PDO::PARAM_STR);
            $stmt->bindValue(':data', $data, PDO::PARAM_STR);
            $stmt->execute();
//            $row_sess_data = $stmt->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

// End of __write()

    /**
     * Destroy
     */
    public function _destroy($id) {

        try {
            $stmt = $db->prepare("DELETE FROM sessions WHERE id = :user_id");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->execute();
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

// End of __destroy()

    /**
     * Garbage Collection
     */
    public function _gc($max) {
        // Calculate what is to be deemed old
        $old = time() - $max;

        try {
            $stmt = $db->prepare("DELETE * FROM sessions WHERE access < :old");
            $stmt->bindValue(':old', $old, PDO::PARAM_STR);
            $stmt->execute();
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

    // End of _gc()
}

class Session
{
    private $db;

    public function __construct($db)
    {    
        $this->db = $db;

这两门课都来自互联网上的真实例子。SavePDO来自PHP.net，会话类来自：

我整天都在试。我的错在哪里？

---

谢谢大家!

您忘了在会话类中添加dsn：

$this->db = new SafePDO;

由于您的构造没有dsn公共函数_构造$dsn的默认值，因此会引发错误。这是正常的

您应该将此dsn提供给会话类，以便能够创建SafePDO isntance

我不知道您是如何使用它们的，但您应该运行第一个脚本，然后在创建会话时执行类似操作：

$session = new Session($db);

然后在会话类中：

class Session {


    private $db;

    public function __construct() {
        // Instantiate new Database object

        $this->db = new SafePDO;

// Set handler to overide SESSION
        session_set_save_handler(
                array($this, "_open"), array($this, "_close"), array($this, "_read"), array($this, "_write"), array($this, "_destroy"), array($this, "_gc")
        );

        // Start the session
        session_start();
    }

    /**
     * Open
     */
    public function _open() {
        // If successful
        if ($this->db) {
            return true;
        }
        return false;
    }

    /**
     * Close
     */
    public function _close() {
        // Close the database
        if ($this->db->close()) {
            return true;
        }
        return false;
    }

    /**
     * Read
     */
    public function _read($id) {


        try {
            $stmt = $db->prepare("SELECT data FROM sessions WHERE id = :user_id");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->execute();
            $row_sess_data = $stmt->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }

        return $row_sess_data['data'];
    }

    /**
     * Write
     */
    public function _write($user_id, $data) {
        // Create time stamp
        $access = time();

        try {
            $stmt = $db->prepare("REPLACE INTO sessions VALUES (:user_id, :access, :data)");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->bindValue(':access', $access, PDO::PARAM_STR);
            $stmt->bindValue(':data', $data, PDO::PARAM_STR);
            $stmt->execute();
//            $row_sess_data = $stmt->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

// End of __write()

    /**
     * Destroy
     */
    public function _destroy($id) {

        try {
            $stmt = $db->prepare("DELETE FROM sessions WHERE id = :user_id");
            $stmt->bindValue(':user_id', $user_id, PDO::PARAM_INT);
            $stmt->execute();
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

// End of __destroy()

    /**
     * Garbage Collection
     */
    public function _gc($max) {
        // Calculate what is to be deemed old
        $old = time() - $max;

        try {
            $stmt = $db->prepare("DELETE * FROM sessions WHERE access < :old");
            $stmt->bindValue(':old', $old, PDO::PARAM_STR);
            $stmt->execute();
        } catch (PDOException $ex) {
            print "<h3>An Error occured!</h3>";
            print $ex->getMessage();
        }
    }

    // End of _gc()
}

class Session
{
    private $db;

    public function __construct($db)
    {    
        $this->db = $db;

您在没有任何参数的情况下构建了SafePDO类的对象：

$this->db = new SafePDO;

但$dsn参数是必需的

你必须设置它。 您应该设置您的数据库用户名

请参见此示例：

$this->db = new SafePDO('mysql:host=localhost;dbname=example_db;', 'example_usr');

---

谢谢大家！我想我有一些进步，但还不确定。现在我看到：致命错误：在第48行的/home/mynshost/public_html/tarrot/db_sessions.inc.php中对非对象调用成员函数prepare致命错误：在第35行的/home/mynshost/public_html/tarrot/db_sessions.inc.php中调用未定义的方法SafePDO:：close in/home/mynshost/public_html/tarrot/db_sessions.inc