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

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...