Zugriff auf Variable in anderer Methode?

$user = new User($userID);

class User {


	public function __construct($userID, $username = null, $email = null) {
		echo "DEBUG1: ".$userID."<br />";
	}


	public function checkPassword($password) {
		global $db;
		$sql = "SELECT 	userID, username, password
			FROM 	x_user
			WHERE 	userID = '".intval($this->userID)."'"; // obsolete: self::$userID
			
		try {
			$recordSet = $db->Execute($sql);
		} catch (exception $e) { 
			var_dump($e); 
			adodb_backtrace($e->gettrace());
		}
		print "DEBUG3: ".$recordSet->fields['password'];
		if ($recordSet->fields['password'] == $password) return 1;
	}
	
	
}

$user->checkPassword($loginPassword)

Notice: Undefined property: User::$initUser in /var/www/htdocs/lib/User.class.php on line 106

Notice: Trying to get property of non-object in /var/www/htdocs/lib/User.class.php on line 106

<?php
/**
 * Manuel Freiholz / www.gainwar.de
 * http://www.tutorials.de/forum/php/293558-zugriff-auf-variable-anderer-methode.html 
 */

class User {

    // Member Variablen
    var $m_id;
    var $m_name;
    var $m_email;

    public function __construct($userID, $username = null, $email = null) {
        echo "DEBUG1: ".$userID."<br />";
        
        $this->m_id = $userID; // Zuweisung der Membervariablen.
    }


    public function checkPassword($password) {
        global $db;
        $sql = "SELECT     userID, username, password
            FROM     x_user
            WHERE     userID = '".intval($this->userID)."'"; // obsolete: self::$userID
            
        try {
            $recordSet = $db->Execute($sql);
        } catch (exception $e) { 
            var_dump($e); 
            adodb_backtrace($e->gettrace());
        }
        print "DEBUG3: ".$recordSet->fields['password'];
        
        // Modifiziert: Setze die Membervariable m_name.
        // Das gleiche sollte auch mit E-Mail passieren.
        if ($recordSet->fields['password'] == $password)
        {
          $this->m_name = $recordSet->fields['username'];
          return 1;
        }
        else
        {
          return 0;
        }
    }
    
    // Funktion um die ID des Benutzers zurückzugeben.
    // Das gleiche sollte auch für die anderen Variablen (name,email) erstellt werden.
    public function getId()
    {
      return $this->m_id;
    }
    
    
}

// --
// TEST
// --

$myUser = new User( 1234 );
echo "Der Benutzer hat die ID: " . $myUser->getId();

?>