Cannot modify header… Not solved by FAQ

Remove twitter tools, then see if the problem exists..

I deleted three unused plugins, no change, it was never specifically to do with Twitter Tools, the error occurs when I add new posts, when I click the ‘more’ tag on the post creator, when I post comments. Virtually any action causes it.

Disable all plugins, and switch to the default theme..

If your installation then functions you know it’s one of two things, either a plugin or the theme, then start enabling one thing at a time until the problem is re-produced..

Also check your config file (wp-config.php) and make sure there’s no extra spaces on the end, after the ending ?>

I should have probably added that I’m new to wordpress and attempting to build a theme.

Its definitely the theme that is at fault. With other themes active it’s fine, and when I empty the functions.php file its fine.

I’ve tried replacing the functions.php file with one from the classic and the default theme and it still doesn’t work :/.

Perhaps I’m writing a functions.php file wrongly? I can’t seem to find any guides as to how they should be written though.

Oh and I checked the wp-config file and there isn’t an ending ?> I unzipped the 2.8.2 WordPress download and the sample doesn’t have an end tag either.

It tells you the error

C:\xampp\htdocs\wordpress\wp-content\themes\clinical\functions.php:1

There’s probably a blank line at the start of that file. Which editor are you looking at it in?

There’s not meant to be a closing ?> at the end of wp-config.

Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\wordpress\wp-content\themes\clinical\functions.php:1) in <b>C:\xampp\htdocs\wordpress\wp-content\plugins\twitter-tools\twitter-tools.php</b> on line <b>1106</b><br />

Its definitely the theme that is at fault.

just like described in the faq ??

DONT use a plain text editor, dont introduce spaces or other ‘stuff’ before the opening <?php

thats precisely what that error suggests is happening.

I’m using Notepad++, I may be new to WordPress but not XHTML/CSS etc.

With the show all characters option selected in Notepad++

https://www.ispycreativity.com/uploads/wordpress-errors/wordpress-functions-php-show-all-chars.jpg

The below images should (hopefully demonstrate that there are no extra characters.

https://www.ispycreativity.com/uploads/wordpress-errors/wordpress-functions-php-top.JPG
https://www.ispycreativity.com/uploads/wordpress-errors/wordpress-functions-php-bottom.JPG

and the functions.php file, saved as phps (I’ve never used this format before).

https://www.ispycreativity.com/uploads/wordpress-errors/functions.phps

If someone manages to resolve this for me I’ll be eternally indebted to them.

Hmm, when the functions.php file is completely empty no errors occur, however when I add just

<?php ?>

the error occurs.

I’ve just started a new theme and I’m still getting the same error even though I swear to god I’m doing it perfectly.

I’m using the latest wordpress version on a local xampp install.

The error I’m getting is:

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\wordpress\wp-content\themes\naturally-dark\functions.php:1) in C:\xampp\htdocs\wordpress\wp-includes\pluggable.php on line 865

Could it be something to do with the fact it says C:\xampp\htdocs\ as opposed to https://localhost/?

2 months later I finally found the solution. Thanks to: https://stackoverflow.com/questions/1067742/clean-source-code-files-of-invisible-characters

The character was a Byte Order Mark “a Microsoft invention to tell, in a Unicode file, in which order multi-byte characters are stored.

To get rid of it, tell your editor to save the file either as ANSI/ISO-8859 or as Unicode without BOM”.

To do this in Notepad++ go Format > Convert to UTF-8 without BOM then Format > Encode in UTF-8 without BOM.

Blue Stunt; thank you for posting your solution to the problem

I downloaded Notepad++ and my problems were totally solved!

Thank you!

Thanks a lot for posting the solution, I just got the same issue after I did a quick fix to a file using notepad…. I’ll never do that again ! ??
— Woods