Automatically append mtime to script and style versions for cache-busting action

gistfile1.php

<?php
/** Automatically append mtime to script and style versions for cache-busting action **/
add_action( 'wp_enqueue_scripts', function() {
	global $wp_styles, $wp_scripts;

	foreach( array( 'wp_styles', 'wp_scripts' ) as $resource ) {

		foreach( $$resource->registered as $name => $registered_resource ) {

			// Not hosted here
			if ( false === stripos( $registered_resource->src, home_url() ) )
				continue;

			$file = str_replace( 'wordpress/', '', str_replace( home_url( '/' ), ABSPATH, $registered_resource->src ) );
			$mtime = filectime( $file );
			$$resource->registered[$name]->ver = $$resource->registered[$name]->ver . '-' . $mtime;
		}
	}
}, 100 );