Compression in load_styles.php does not always work, causing inability to use the admin

[cfeet77]

I think this is quite important, because it sometimes prevents using wp-admin pages altogether.

Server environment: Debian Linux 6.0.5, apache 2.4.2, mysql 5.5.27, php 5.4.5.

I have discovered that sometimes my admin Console pages are not rendered properly, as though a style sheet is not loaded. This does not depend on a browser and client operating system. I tried IE, Firefox, Chrome, Opera, I tried client browser in Windows XP, Windows Vista, Android 4.1.2, and the problem could be seen in all these cases.

The problem is random. Through some magick and without any special activity on my side, wp-admin pages sometimes stop working as described, and after 10 minutes it randomly fixes itself (or does not), again without any action on my side.

Further investigation showed that when I manually try to open a link containing load-styles.php as referred to from the console page (I copy and paste the link including all GET request variables into a new browser window), then sometimes garbage is shown for the load-styles.php. Encoding is UTF-8 (I have added .htaccess just in case to make sure this is not an issue). But when garbage is shown, then admin pages do not work (their stylesheet obviously does not get loaded). When there is no garbage in load-styles.php (i.e. normal stylesheet, good visible text), then all is good.

I had a faint idea that this was because I mechanically moved my site from one URL (approx. localhost) to a "production-level" URL (copied all files + database), I thought this could be related (even though I changed all URLs in Settings/General afterwards), but this did not hold water.

So looked into load-styles.php and noticed there is some conditional content encoding out there. What I did I disabled this content encoding altogether like this:

if ( $compress && ! ini_get('zlib.output_compression') && 'ob_gzhandler' != ini_get('output_handler') && isset($_SERVER['HTTP_ACCEPT_ENCODING']) ) {
	header('Vary: Accept-Encoding'); // Handle proxies
	if ( false !== stripos($_SERVER['HTTP_ACCEPT_ENCODING'], 'deflate') && function_exists('gzdeflate') && ! $force_gzip ) {
		// header('Content-Encoding: deflate');
		// $out = gzdeflate( $out, 3 );
	} elseif ( false !== stripos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') && function_exists('gzencode') ) {
		// header('Content-Encoding: gzip');
		// $out = gzencode( $out, 3 );
	}
}

and now everything works. All fine and all good, problem solved. No garbage anymore.

Would please bother to disable this worse than useless content compression in load-styles.php for the time being before you find a solution that works for all? I believe I might be not the only one to experience these random issues with Console stylesheet. I expect that 99% of website admins have fast connections to manage their websites, and for those who do not, Opera Mini is still there and still working.

And I also mean that the problem, once it shows up, is persistent, i.e. it does not disappear through a trivial full page reload (Ctrl-Shift-R in FF, for instance). If pages (stylesheet) stop working, then nothing helps: not clearing the browser cache, not restarting the browser, not starting a new instance of the browser, not starting another browser from another vendor. So the problem is not on the client side, it is on the server side.

[SergeyBiryukov]

You can add define('CONCATENATE_SCRIPTS', false); to your wp-config.php file as a workaround instead of editing core files: ​http://codex.wordpress.org/Editing_wp-config.php#Disable_Javascript_Concatenation.