PHP session error in some pages

Question

I have written <?php session_start(); ?> above everything in all pages. Some pages are rendering fine but I am getting this error in other pages. I have checked and matched each page code and code is fine. If I remove <?php session_start(); ?> then page renders fine but I need to use session.

Cannot send session cache limiter - headers already sent (output started at /home/) in ...

One thing to note is: It runs fine on my local server.

I am including file but after this session_start(). yes its headers already sent — Muhammad Imran Tariq, May 31 '13 at 15:18
@ImranTariq - can you edit the question, and include the full error message? It should tell you exactly where the output was started. — andrewsi, May 31 '13 at 15:19
I would recommend instead of placing `session_start()` in 1 million files, to put it in one main `setup.php` file which would set everything up for the page, such as sessions, classes, functions, etc. then you would potentially only have to debug 1 file. — Get Off My Lawn, May 31 '13 at 15:21
Do you have any whitespace (spaces/tabs/newlines/etc) before the `session_start()`? — Get Off My Lawn, May 31 '13 at 15:24

score 0 · Answer 1 · answered May 31 '13 at 15:19

I would bet it's one of two things:

Make sure there is no output, including newlines, in your file before you call session_start. PHP must send HTTP headers first (before the message body, i.e. page content), so trying to send a header after you've already sent page content will give you that error.
You should only call session_start only once per page. If you're using include in a file after you've called session_start, make sure you're not calling session_start again in the included file. This would cause the "headers already sent" error.

there is no output and it is being called one time – Muhammad Imran Tariq May 31 '13 at 16:00 — Muhammad Imran Tariq, May 31 '13 at 16:00

score 0 · Answer 2 · answered May 31 '13 at 15:19

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you have some output (maybe an whitespace) in one of your included files.

maybe your <?php is not the very first of your file somewhere.

answered May 31 '13 at 15:19

steven

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score 0 · Answer 3 · answered May 31 '13 at 15:23

You could also try to use output buffering (http://php.net/manual/es/function.ob-start.php). I'd first check to see whether you are not sending any output by mistake (as @steven suggests), but still, it might be a good idea for you to buffer your outputs.

score 0 · Answer 4 · answered May 31 '13 at 15:24

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Since you are including multiple files, and you seem to have a session_start() in multiple files, I bet the error is thrown in the second file.

Check all files for the session_start(), and for whitespace before any of these are called.

answered May 31 '13 at 15:24

Sablefoste

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score 0 · Answer 5 · answered May 31 '13 at 15:25

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This is a very typical BOM header problem. I suspect that your editor stored a UTF-8 BOM header with 3 bytes ï»¿ at the begin of the file. The editor will hide them, so if you are not sure if your file contains these characters, you can either use a non interpreting editor (hex editor), or this wonderful online W3C checker.

answered May 31 '13 at 15:25

martinstoeckli

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good text editors will let you save a file with no bom, too – user428517 May 31 '13 at 15:27
@sgroves - Absolutely, if this is indeed the problem, the next step would be to look for the proper settings in the editor options. – martinstoeckli May 31 '13 at 15:29

PHP session error in some pages

5 Answers5