WordPress editor style cache refresh plugin

esrjl-editor-styles-refresh.php

<?php
/**
 * Plugin Name: Editor Styles Refresh
 * Plugin URI: https://gist.github.com/elusiveunit/f0f728771de6647778fa
 * Description: Adds file time query string to theme editor style URLs, to force cache busting when the file is changed.
 * Author: Jens Lindberg
 * Version: 0.1
 * License: GPL-2.0+
 */

/**
 * Add query string with file modification timestamp to theme editor style
 * files.
 *
 * @param string $css Comma separated stylesheet URIs.
 * @return string
 */
function esrjl_refresh_editor_styles_sweet_unique_func_name_bro( $css ) {
	$files = explode( ',', $css );
	$tpl_uri = get_template_directory_uri();
	$style_uri = get_stylesheet_directory_uri();

	foreach ( $files as $file_url ) :

		// Not a theme file, skip it
		if ( false === strpos( $file_url, $tpl_uri )
		  && false === strpos( $file_url, $style_uri ) )
			continue;

		$file_data = parse_url( $file_url );
		$file_path = ( ! empty( $file_data['path'] ) ) ? $file_data['path'] : '';

		// Assuming this could fail on some server setups
		$file_full_path = ( $file_path ) ? $_SERVER['DOCUMENT_ROOT'] . $file_path : '';

		if ( empty( $file_data['query'] )
		  && $file_full_path
		  && file_exists( $file_full_path ) ) :
			$mod_time = filemtime( $file_full_path );

			// Add modification timestamp query string
			if ( is_int( $mod_time ) ) :
				$css = str_replace(
					$file_path,
					"{$file_path}?ver={$mod_time}",
					$css
				);
			endif;
		endif;
	endforeach;

	return $css;
}
add_filter( 'mce_css', 'esrjl_refresh_editor_styles_sweet_unique_func_name_bro' );