PHP Session Writing to Database

[TheFireBat]

I'm struggling to get PHP to write sessions to a database. My issue is that when I override the session handler and proceed to call session_start() I get an error message telling me that the headers were already sent. I've been reading for days with no results.

 

Common issues that pop up are the BOM and whitespace. I used vi to double check if I have a BOM, which I don't. As for whitespace, I don't see any in my code. However, for testing purposes I removed all blank lines and all tabs. I'll add formatting back in once I solve the issue, but for now, I removed it all. I don't think whitespace is my issue.

 

The other reason I don't think whitespace is my issue is reading the error message from phpdbg.

[PHP Warning:  session_start(): Cannot send session cookie - headers already sent in /usr/local/apache2/htdocs/index.php on line 43]
[PHP Stack trace:]
[PHP   1. {main}() /usr/local/apache2/htdocs/index.php:0]
[PHP   2. session_start() /usr/local/apache2/htdocs/index.php:43]
[PHP Warning:  session_start(): Cannot send session cache limiter - headers already sent in /usr/local/apache2/htdocs/index.php on line 43]
[PHP Stack trace:]
[PHP   1. {main}() /usr/local/apache2/htdocs/index.php:0]
[PHP   2. session_start() /usr/local/apache2/htdocs/index.php:43]

If I turn on verbose mode in phpdbg the line before the error is:

[L4           0xb73454f4 ZEND_RETURN                    C0                   <unused>             <unused>             /usr/local/apache2/htdocs/index.php]

Based on the code I provide below, line 4 is in the open function and is the return value. Line 43 is session_start(). This is where I'm confused. The error message is telling me calling session_start assigns the header and the open function is also trying to assign a header?

 

From what I understand, the session handler's first call is to the open function. Open is being called, I just don't get why both open and session_start are trying to send headers separately. I don't see any whitespace, there is no BOM. I must be doing something wrong with the session handler?

<?php
$db = pg_connect ( "host='' port='' dbname = '' user='' password=''" );
function open() {
return true;
}
function close() {
return true;
}
function read($id) {
$stmt = 'SELECT data FROM sessions WHERE id = \'' . $id . '\'';
$result = pg_query($stmt);
$numrows = pg_num_rows($result);
if( $numrows > 0 ) {
$row = pg_fetch_array($result, 0, PGSQL_ASSOC);
return $row['data'];
} else
return '';
}
function write($id, $data) {
$access = time();
$stmt = 'REPLACE INTO sessions VALUES (\'' . $id . '\', ' . $access . ',\'' . $data . '\')';
$result = pg_query($stmt);
if( $result)
return true;
return false;
}
function destroy($id) {
$stmt = 'DELETE FROM sessions WHERE id = \'' . $id . '\'';
$result = pg_query($stmt);
if( $result )
return true;
return false;
}
function gc($max) {
$old = time() - $max;
$stmt = 'DELETE * FROM sessions WHERE access < ' . $old;
$result = pg_query($stmt);
if( $result )
return true;
return false;
}
session_set_save_handler("open", "close", "read", "write", "destroy", "gc");
session_start();
?>

Note, I'm also attaching the file with the code as well.

index.php

[TheFireBat]

1) REPLACE INTO is not PostgreSQL compatible. I modified the code to instead use:

		$stmt = 'SELECT data FROM sessions WHERE id = \'' . $id . '\'';
		$result = pg_query($stmt);

		$numrows = pg_num_rows($result);
		if( $numrows > 0 ) {
			$stmt = 'UPDATE sessions SET (id, access, data) = (\'' . $id . '\', ' . $access . ',\'' . $data . '\')';
		}
		else {
			$stmt = 'INSERT INTO sessions (id, access, data) VALUES (\'' . $id . '\', ' . $access . ',\'' . $data . '\')';
		}

2) My session now works in Firefox, but phpdbg still complains about the headers. I never tried it in browser because I was focused on getting rid of errors in phpdbg before hand. I verified it's working by going into the database and seeing the test session variable I added increment as I refresh.

 

3) This now begs the question, what is phpdbg doing? Why is phpdbg sending headers where my browsers, both Chrome and Firefox, do not? Can I fix/configure phpdbg to work properly?

 

Here is how I am running phpdbg. 

cd /usr/local/apache2/htdocs
phpdbg
phpdbg> exec index.php
phpdbg> run

I imaigne there is an issue with how I am running phpdbg?

[mac_gyver]

yes, your errors are due to the debugger. php code debuggers generally work by adding a layer of output buffing to send the debugging information to their client module.

 

you should generally only use a debugger to debug why your code isn't doing what you expect (that's why they are called debuggers), not as the primary method of running your code.

[TheFireBat]

I started in the browser but moved to using phpdbg once I started having errors show up. Once I was in phpdbg I didn't plan to move out until I removed all errors. So I started with quite a few errors and had dwinled it down to just the remaining errors with the headers. Not knowing any better, I should have gone back to the browser once I was down to just the headers.

 

I will definitely know better for next time. I am new to PHP and didn't know that the debugger was adding an extra layer and modifying/sending headers.

 

Thank you for clearing that up.

[singhRahul34]

hello sir, 

actually i have started session in a page and i want to know if i login from index.php it take me to home.php(where i have started a session ) if i give a url index.php it redirects me to that page but i want to use session which doesnot redirect me to that page unless until i dont logout from that page 

try to help me please