Custom version querystring appending for WordPress JS and CSS assets

cac-asset-ver.php

<?php
/**
 * Note that CAC_VERSION is a custom constant. Replace as necessary.
 */
function cac_asset_ver( $tag, $handle, $src = '' ) {
	// 'style_loader_tag' doesn't pass a src, so we sniff it from the tag.
	if ( ! $src ) {
		preg_match( '/href\=\'([^\']+)\'/', $tag, $src_matches );
		if ( $src_matches ) {
			$src = $src_matches[1];
		}
	}

	$_src = parse_url( $src );
	if ( $_src['query'] ) {
		wp_parse_str( $_src['query'], $vars );
		foreach ( $vars as $k => &$v ) {
			if ( 'ver' !== $k ) {
				continue;
			}

			$v .= '-' . CAC_VERSION;
		}

		$new_path_and_query = add_query_arg( $vars, $_src['path'] );
		$tag = str_replace( $_src['path'] . '?' . $_src['query'], $new_path_and_query, $tag );
	}

	return $tag;
}
add_filter( 'script_loader_tag', 'cac_asset_ver', 10, 3 );
add_filter( 'style_loader_tag', 'cac_asset_ver', 10, 2 );