WordPress snippet: Add version to CSS/JS files automatically

functions.php

<?php
function my_file_version( $file ) {
	global $wp_version;

	$version = $wp_version;

	if ( file_exists( $file ) ) {
		$version = filemtime( $file );
	}

	return (string) $version;
}

function my_version_js_css( $src ) {
	$parts = explode( '?', $src );
	$result = $parts[0];
	if ( strpos( $result , home_url() ) !== false ) {
		$result = preg_replace_callback( '#(.*?)((\.min)?\.(css|js))$#', function( $match ) {
			$file = str_replace( home_url(), ABSPATH, $match[0] );
			if ( file_exists( $file ) ) {
				return $match[1] . $match[2] . '?v=' . my_file_version( $file );
			} else {
				return $match[0];
			}
		}, $result );
	}
	return $result;
}
add_filter( 'script_loader_src', 'my_version_js_css', 12, 1 );
add_filter( 'style_loader_src', 'my_version_js_css', 12, 1 );
add_filter( 'stylesheet_uri', 'my_version_js_css', 12, 1 );