CODEWITHSUNDEEP
phpsession
Bryan
Bryan

Reputation: 3494

Alternating class not found error when using session handler

First of all, if it's relevant, this is in a session handler. This function is the one that writes to the database and is passed to session_set_save_handler along with my other functions like this

session_set_save_handler('sess_open', 'sess_close', 'sess_read', 'sess_write', 'sess_destroy', 'sess_gc');

I have this chunk of code...

$qid = "select count(*) as total
        from zen_sessions
        where sesskey = '" . $key . "'";

if(!class_exists('DB'))
    require_once dirname(dirname(__FILE__)).'/class/DB.class.php';
var_dump(new DB());                      //this is line 109
$total = DB::select_one($qid);

the conditional and var_dump are for testing. Oddly enough sometimes it works fine while others it gives me an error:

Fatal error: Class 'DB' not found in /path/to/file/session_functions.php on line 109

I cannot figure how this wouldn't crash at the require instead of the var_dump and why only sometimes?

Thanks in advance for any insight.

edit-- response to comment/question:

The result of the following code

var_dump(class_exists('DB', false)); 
var_dump(is_file(dirname(__DIR__).'/class/DB.class.php'));

is:

bool(false) bool(true)

before trying to require it and the same result after the require(or true true when it doesn't give me an error) Looks something like:

bool(true) bool(true) object(DB)#3 (0) { }

The previous code chunk is the result about once out of every 5 page loads while the error is the result the other 4.

Edit2 -- new findings.

Even more curious is according to the manual I should never see these debugging statements or errors

Note:

The "write" handler is not executed until after the output stream is closed. Thus, output from debugging statements in the "write" handler will never be seen in the browser. If debugging output is necessary, it is suggested that the debug output be written to a file instead.

Edit 3 - A Note for clarity:

The DB class Should have been autoloaded(and is everywhere else in the application) the class_exists and require are simply there for testing purposes.

Edit 4 - Stack trace

I decided to try and throw an exception when the class isn't found to see the stack trace, this is what I get

Fatal error: Uncaught exception 'Exception' with message 'DB Class Not Found.' 
in /path/to/file/session_functions.php:108 
Stack trace: #0 [internal function]: sess_write('074dabb967260e9...', 'securityToken|s...') 
#1 {main} thrown in /path/to/file/session_functions.php on line 108

Upvotes: 2

Views: 766

Answers (3)

Mehran
Mehran

Reputation: 16861

Even though I can not be sure, but I bet that the error is somewhere else and it's just projecting itself as you've described it.

In order to test and debug your code, you need to use a debugger like PDT. But then the problem is that you need to debug a part of your code that is out of debugger's reach, the session writer! To overcome this problem you can use session_write_close. You can put it somewhere at the end of your bootstrap or if you don't have one, you can do it like this:

<?php
function shutdown_function()
{
    session_write_close();
}

register_shutdown_function('shutdown_function');

Then by setting a break point, you can start debugging your session code from here. Let me know if I win the bet.

Upvotes: 1

dave
dave

Reputation: 64657

The only thing that I can think of that may be causing this, is from a notice in the PHP docs for session_set_save_handler:

Warning

Current working directory is changed with some SAPIs if session is closed in the script termination. It is possible to close the session earlier with session_write_close().

From what you are experiencing, I am guessing the current working directory is changed, so require_once doesn't find the file.

I would try adding session_write_close(); to somewhere in your function and see if that fixes it.

Admittedly, not sure why is_file would return true in this case, but maybe worth a shot.

Upvotes: 1

r3wt
r3wt

Reputation: 4742

try:

$save_handler = new DB();
session_set_save_handler($save_handler, true);

then map read, write, etc functions inside your class. i faced a similar issue(bizarre random errors about a class not being found) implementing another user's custom save handler workaround for HHVM with redis, and this is how i fixed it. if you are using HipHopVirtualMachine (or possibly some other type of JIT compiler or app cache), sometimes your project can cache some functions without updating, producing odd errors like this. usually a restart of the fastcgi daemon and adding white space to one of your files is enough to force it to re interpret your project.

Upvotes: 0

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