Disable the server cache
In order to disable the cache in the server and let the files be served each time, disable PageSpeed for Apache and OPCache for PHP, enabled by default.
To disable PageSpeed, comment out the following lines in your httpd.conf (installdir/apache2/conf/httpd.conf)
#Include conf/pagespeed.conf #Include conf/pagespeed_libraries.conf
To disable OPCache, change opcache.enable in your php.ini file and set it to 0 (installdir/php/etc/php.ini)