https caching of resources used by main php script, NOT the script itself

Question

I'm a little confused here. I read some of the earlier questions on https caching but I didnt get a clear answer.

I've got a script sitting on: https://www.example.com/main.php

It generates an html page that refers to images/css/js resources sitting (relatively) at: /css /javascript /images /a/b/img2

How do I enable caching for these resources?? I have access to modifying the header output of the main.php script.

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Edit: Solution as below:

#Set a far expiration date for components
<ifmodule mod_expires.c>
ExpiresActive On
  <filesmatch "\.(jpg|jpeg|gif|png|css|js)$">
       ExpiresDefault "access plus 6 months"
   </filesmatch>
</ifmodule>

#add ETag for components
FileETag MTime Size

Answer 1

If you're running Apache web server you probably need a .htaccess file to enter caching information about your components.

In the .htaccess file:

#Set a far expiration date for components
<ifmodule mod_expires.c>
ExpiresActive On
ExpiresByType image/gif A2592000
ExpiresByType image/png A2592000
ExpiresByType image/jpg A2592000
ExpiresByType image/jpeg A2592000
  <filesmatch "\.(jpg|gif|png|css|js)$">
       ExpiresDefault "access plus 10 years"
   </filesmatch>
</ifmodule>

#add ETag for components
FileETag MTime Size

Access to header output of the main.php script can only modify caching for your main script, not the components.