Function - Cachebuster - Add timestamp to assets in order to break out of browser caching

dev_script_asset_cachebuster.php

<?php

if (!function_exists('addTimestamp')) {
	function addTimestamp($src, $remote = false, $man_v = '') {
		if (empty($src)) {
			return;
		} elseif ($_SERVER['HTTP_HOST'] === $_SERVER['SERVER_NAME']) {
			$local_root = $_SERVER['DOCUMENT_ROOT'] . '/';
			
			preg_match('/^([https]+:)?\/\//', $src, $src_proto);
			$src_proto = (isset($src_proto[0])) ? $src_proto[0] : '';
			
			$local_domain = $src_proto . $_SERVER['SERVER_NAME'] . '/';
			$local_file = realpath(str_replace($local_domain, $local_root, $src));
			if (file_exists($local_file)) {
				return $src . '?v=' . date('Ymd.His', filemtime($local_file)) . $man_v;
			}
			
			if ($remote) {
				$src_rewrite = preg_replace('/^\/\/|^(?!https?:)/', 'https://', $src);
				$remote_file = get_headers($src_rewrite, 1);
			
				if (isset($remote_file['Last-Modified'])) {
					return $src . '?v=' . date('Ymd.His', strtotime($remote_file['Last-Modified'])) . $man_v;
				} elseif (isset($remote_file['Etag'])) {
					return $src . '?v=' . $remote_file['Etag'] . $man_v;
				}
			}
		}
		
		return ($man_v) ? $src . '?v=' . $man_v : $src;
	}
}