How do I enable mod_deflate for PHP files?

Question

I have a Liquid Web VPS account, I've made sure that mod_deflate is installed and running/active.

I used to gzip my css and js files via PHP, as well as my PHP files themselves... However, I'm now trying to do this via mod_deflate, and it seems to work fine for all files except for PHP files. (Txt files work fine, css, js, static HTML files, just nothing that is generated via a PHP file.) How do I fix this?

(I used the "Compress all content" option under "Optimize Website" in cPanel, which creates an .htaccess file in the home directory (not public_html, one level higher than that) with exactly the same text as the "compress everything except images" example on http://httpd.apache.org/docs/2.0/mod/mod_deflate.html)

.htaccess file:

<IfModule mod_deflate.c>
    SetOutputFilter DEFLATE
    <IfModule mod_setenvif.c>
        # Netscape 4.x has some problems...
        BrowserMatch ^Mozilla/4 gzip-only-text/html

        # Netscape 4.06-4.08 have some more problems
        BrowserMatch ^Mozilla/4\.0[678] no-gzip

        # MSIE masquerades as Netscape, but it is fine
        # BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

        # NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
        # the above regex won't work. You can use the following
        # workaround to get the desired effect:
        BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html

        # Don't compress images
        SetEnvIfNoCase Request_URI .(?:gif|jpe?g|png)$ no-gzip dont-vary
    </IfModule>

    <IfModule mod_headers.c>
        # Make sure proxies don't deliver the wrong content
        Header append Vary User-Agent env=!dont-vary
    </IfModule>
</IfModule>

Answer 1

PHP files usually serves text/html content (although you can also generate images and pretty much everything). PHP files are never sent to the client: it gets processed to generate content (text/html or images). You're looking to gzip this content.

Answer 2

You can add zlib.output_compression = On to your php.ini configuration file. This will compress the output regardless of mod_deflate.

Answer 3

That whole config is way obsolete. It can and should be deleted now: Netscape 4 hasn't been around for a long time, and setting Vary: User-Agent unnecessarily hinders caching.

The only mod_deflate config you need is one line to turn deflate on for compressible media types, either using AddOutputFilter to choose compressible files by extension, or AddOutputFilterByType to choose them by returned Content-Type.

Answer 4

It's been a while since I posted this question - I ended up enabling zlib compression via PHP.ini so zlib compresses PHP output while mod_deflate compresses everything else.

I'm thinking the reason it wasn't working (mod_deflate wasn't compressing PHP output) has to do with PHP running as CGI and not an Apache DSO...