How add Expires headers on Css.php file (Scaffold) - php

Question

I use SocialEngine for my website, I want to speed my website so I have use Gtmetrix and PageSpeed to see what I can improve
I see that Add Expires headers have 0/100 ..
I have do research but how I can add on Exprires headers my CSS that look like this ..
https://www.exemple.com/application/css.php?request=application%2Fthemes%2Fmytheme%2Ftheme.css&c=2174&pageStart=332433&pageEnd=85951
https://www.exemple.com/application/css.php?request=application%2Fthemes%2Fmytheme%2Ftheme.css&c=2174&pageStart=667827&pageEnd=345656
https://www.exemple.com/application/css.php?request=application%2Fthemes%2Fmytheme%2Ftheme.css&c=2174&pageStart=1019386&pageEnd=6576458
How I can do ? Thank you
My .htaccess:
<IfModule mod_expires.c>
# Enable expirations
ExpiresActive On
# Default directive
ExpiresDefault "access plus 1 month"
# My favicon
ExpiresByType image/x-icon "access plus 1 year”
# Images
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/jpg "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
# CSS
ExpiresByType text/css "access 1 month”
# Javascript
ExpiresByType application/javascript "access plus 1 year"
</IfModule>
Themes /application/themes/* We utilize a framework called CSS
Scaffold which makes editing your community's theme a simple process.
Each theme is stored in its own directory within
/applications/themes/. A default theme is automatically loaded when
you first install SocialEngine. Each theme contains two files:
constants.css and theme.css.
At the top of constants.css, you'll find a series of global CSS
settings (called "constants"). You can edit these to adjust the
colors, fonts, and other styles throughout your entire community.
The other file, theme.css, contains more specific styles that are used
throughout your community. Many of these styles inherit values from
constants.css. If you want to override any of the default styles on
your community, you can edit them here. If they aren't present in
theme.css (and are being loaded from outside the theme itself), you
can override them by adding new styles to the bottom of theme.css.
More information about how to work with CSS Scaffold is available on
Github or Google for CSScaffold for videos and tutorials.

Answer 1

You already have configured
ExpiresByType text/css "access 1 month”
so CSS files should have the correct header.
It seems, that application/css.php delivers the appropriate CSS file. In order to trigger the expires header, the script must also set the correct mime type for the CSS files returned.
This can be accomplished with a header of Content-Type
header('Content-Type: text/css');
Alternatively, you could also add your own Expires header, e.g.
$plus_month = date('r', strtotime('+1 month'));
header("Expires: " . $plus_month);