# Set far-future expiry for images, css, and js
# Remember that you MUST change the filename whenever you update these items!
<ifmodule mod_expires.c>
<filesmatch "\.(jpg|jpeg|png|gif|js|css)$">
ExpiresActive on
ExpiresDefault "access plus 10 years"
</filesmatch>
<filesmatch "\.(ico)$">
ExpiresActive on
ExpiresDefault "access plus 2 months"
</filesmatch>
</ifmodule>

http://www.thewebsqueeze.com/articles/yslow-going-from-f-to-a.html/2/

set expire for files in apache

apache

PHP