PHP/HTML/CSS: IE acting weird when using require_once()

Question

Now this is the most weird problem I've ever had in PHP.

All pages looks normal except one; when I first saw the problem I thought it was one of these common problems with IE and stylesheets (I've got a specific CSS-file on this page). I tried to exclude the CSS-file just to ensure that the problem really was in this file, but it wasn't. Then I thought I had forgotten to close any HTML tag, so I went through the code multiple times, but all seemed to be correct. So I started to put code in comments and compare with IE until I realized that when I putted the following code in a comment, the page itself acted normal:

require_once(PATH_INCLUDES . 'adjacency.php');

It's a valid path, and the file does just contain a class with functions - there's no output in any way except die() if a MySQL query fails.

Some things that look weird in IE are the following:

• The container is normally centered, now it's at the left.
• A background with repeat-x doesn't go all the way.
• The hover functionality in the menu doesn't work.

Anyone?

Edit: I tried to include adjacency.php in another file, and the same problem occurred.

Answer 1

As a guess, there's most likely some space at the end of the include file after the closing "?>". (One of the reasons that Zend Framework recommends not using the closing PHP tag.)

Answer 2

Does the included PHP file begin with a UTF-8 BOM (byte order mark)? This is an invisible byte sequence that sometimes appears at the beginning of a Unicode text file to aid auto-detection of the UTF. Unfortunately, PHP is somewhat naive, and will output the BOM as and when it reads it in from an included PHP file. By my experiment, IE can handle one BOM, but if the BOM is doubled (as will be the case if the PHP file the browser requested and one included each contain the BOM) then it fails to see the doctype as being at the beginning and thus quirks mode is triggered.

Make sure your editor is configured to save without BOMs.