Blank line in RSS feed

usually this issue is from a blank line at the top or bottom of a module file. This is the reason why it's recommend not to put the closing ?> in your module files as a space can sometimes sneak in at the end.

This can be a HUGE pain to sort out, especially if you have a lot of custom modules. Here's how to find the culprit:

In your module.inc file (in the includes folder) add this after the drupal_load function in the module_load_all function

print $module.'|';

You'll get a huge mash of modules, but the one that starts on line 2 will be your culprit module

Hi, I just had a problem with having a blank line at the beginning of a page too (just before the DOCTYPE declaration). This caused the

Invalid xml declaration.
 Line: 2 Character: 3

error message when accessing the rss.xml page. This is often caused by having a blank line before the opening ?php tab in some of your *.module file. Here is a "how to" for finding the *.module that causes the blank line.

First, let me explain the logic behind the blank line. Drupal generates the page at some point. In case there is some piece of code that includes something outside PHP, it gets sent to the browser sooner than the page is generated by Drupal. And this is the blank line in our case. So, in order to find the code that sends something to the browser sooner than the whole page is put together by Drupal, you can switch off output buffering and let the site generate a warning for you. Go to your php.ini and uncomment the output_buffering parameter. This will turn off the buffer at the server and cause the server to send stuff to the browser as it generates it, the server will not wait until the whole page is put together to send it. Restart the server. This will cause a warning at your site similar to the following:

warning: Cannot modify header information - headers already sent by (output started at C:\User\web\WWW_ROOT_80\sites\all\modules\similar\similar.module:2) in C:\User\web\WWW_ROOT_80\includes\common.inc on line 148.

This message tells you that there is something on line 2 in similar.module that is sent to the browser before the page is completed by Drupal and headers are sent (most likely it will be some other module in your case, I had an error in similar.module through my fault). This is your perpetrator.

PS: You might need to clear your cache (both browser and Drupal) to get the warning after disabling output buffering.

My site Maxi-Pedia

Anyone reading this, my problem having a blank line above the content of my feed ended up being caused by a blank line at the top of my index.php file. One more thing to check if this helps.

The template might also be an issue. In my case there were trailing spaces at the end of sites/all/themes/BRANDNAME/template.php.

I found the culprit module using the technique described, ie

// from module.inc 
foreach (module_list(TRUE, $bootstrap) as $module) {
      drupal_load('module', $module);
      print $module.'|';

Nothing was wrong with the module though, no extra space, no closed PHP ?>. What I found worked, strangely enough, was SSHing into the remote server, and retyping just the the opening greater than sign using Vim, ie the < in <?php. Reload page. Valid XML. Crazy.

I have tried the above, but it doesn't seem to be in the modules or theme, I notice the code on the site starts a line lower so whatever it is it's on every page and driving my client insane.

Thank you for the tip on the template.php file. That is where I found the problem, and probably never would have found it, had you not mentioned it.

I resolved it by simply remove all the php closing tags ?> at the end of custom module files i.e .module file

In my Case it was the Rebuild theme registry and output template debugging on every page Option in a Zen Subtheme. Just switched it off

This approach helped in my case:

If you are using phpstorm - or any other capable IDE - use regex search with the below snippet. In phpstorm simple use the "Find in Path" and search within your custom module directory.
^\s *<\?php

Use the "File mask" option to narrow down the search to *.module files. I found two modules that had a white space before the opening PHP tag causing the issue.

I hope this helps someone.

Changing theme debug to false in settings.php solved this for me,

$conf['theme_debug'] = FALSE;