#23354 [NEW]: Use of variable before registration problem

From: Date: Fri, 25 Apr 2003 22:22:15 +0000
Subject: #23354 [NEW]: Use of variable before registration problem
Groups: php.bugs 
Request: Send a blank email to php-bugs+get-38424@lists.php.net to get a copy of this message 
From:             bill dot macallister at prideindustries dot com
Operating system: Linux 2.4.18-27.7.xsmp
PHP version:      4.3.1
PHP Bug Type:     *General Issues
Bug description:  Use of variable before registration problem

This is as much a change in behavior as anything, but the
specific failure seems to indicate a deeper problem.

We have an application that uses out own session save handler
to store session data in a MySQL database.  This application
has been in use on a 4.2.1 system for months now.  When I 
upgraded our test system to 4.3.1 we started getting failures.
The exact error was a MySQL connection failure because of
bad authentication credentials.  The error report indicated
that the connection attempt was for webuser@localhost.  Our
Apache server runs as webuser so this is the default user.
The code generating this message is:

  $mysql_host = 'mysql-master';
  $mysql_user = 'phpuser';
  $mysql_pass = 'phppass';
  $mysql_db   = 'php_sessions';
  if ($cnx = mysql_connect ($mysql_host, 
                            $mysql_user, 
                            $mysql_pass)) {
    if ($db = mysql_select_db($mysql_db, $cnx)) {
      $ret = $cnx;
    }
  }

So, the error message really is bogus or PHP's heap is 
corrupt.

It turns out that I was able to make the error go away
by changing the code:

  $s_user_id = $user_data["user_id"];
  session_register("s_user_id");

to:

  session_register("s_user_id");
  $s_user_id = $user_data["user_id"];

It appears that in 4.2.1 you can use variables before you
register then and in 4.3.1 you cannot.

The 4.3.1 behavior is at least a bug in that PHP silently
accepts the invalid instruction sequence and corrupts its
environment so that completely unrelated parts of the 
script will fail.  If registration is required before use
I would really like to see session_register complain if
you try and do it wrong.

Bill
-- 
Edit bug report at http://bugs.php.net/?id=23354&edit=1
-- 
Try a CVS snapshot:         http://bugs.php.net/fix.php?id=23354&r=trysnapshot
Fixed in CVS:               http://bugs.php.net/fix.php?id=23354&r=fixedcvs
Fixed in release:           http://bugs.php.net/fix.php?id=23354&r=alreadyfixed
Need backtrace:             http://bugs.php.net/fix.php?id=23354&r=needtrace
Try newer version:          http://bugs.php.net/fix.php?id=23354&r=oldversion
Not developer issue:        http://bugs.php.net/fix.php?id=23354&r=support
Expected behavior:          http://bugs.php.net/fix.php?id=23354&r=notwrong
Not enough info:            http://bugs.php.net/fix.php?id=23354&r=notenoughinfo
Submitted twice:            http://bugs.php.net/fix.php?id=23354&r=submittedtwice
register_globals:           http://bugs.php.net/fix.php?id=23354&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=23354&r=php3
Daylight Savings:           http://bugs.php.net/fix.php?id=23354&r=dst
IIS Stability:              http://bugs.php.net/fix.php?id=23354&r=isapi
Install GNU Sed:            http://bugs.php.net/fix.php?id=23354&r=gnused

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