During WordPress theme or plugin development, when working on stylesheets, it’s sometimes useful to add a version number to a CSS file so that the browser will load the updated version rather than using the cached version.
For a CSS file that is linked or enqueued directly, this is straightforward, but what about the right-to-left support rtl.css that is loaded automatically when present?
Here’s a quick snippet that appends a version number based upon the file modification date:
<?php /* Break Cache of rtl.css when it is updated */ add_filter( 'locale_stylesheet_uri', function ($localized_stylesheet_uri) { $time_ver = filemtime( get_stylesheet_directory() . '/rtl.css' ); return add_query_arg( array('ver' => $time_ver), $localized_stylesheet_uri ); }); ?>
Source: Stackexchange