combine js/css from cdn services

cdn.php

<?php
/**
 * cdn proxy for cdnjs/jsdelivr/unpkg/...
 *
 * @author   sskaje
 * @usage    https://p.rst.im/(js|css)/cdnjs:/path1;/path2;unpkg:/path3;/path4
 * @example  https://p.rst.im/css/cdnjs:/bootswatch/4.5.0/darkly/bootstrap.min.css;/bootstrap-select/1.13.18/css/bootstrap-select.min.css
 * @example  https://p.rst.im/js/cdnjs:/jquery/3.4.1/jquery.min.js;/twitter-bootstrap/4.5.0/js/bootstrap.bundle.min.js;/datatables/1.10.21/js/jquery.dataTables.min.js
 */

$request_uri = $_SERVER['REQUEST_URI'];
$max_resource= 20;
$ttl = 86400 * 30;

$file_mode = 'auto';
if (strpos($request_uri, '/css') === 0) {
	$request_uri = substr($request_uri, strlen('/css/'));
	$file_mode = 'css';
} else if (strpos($request_uri, '/js') === 0) {
	$request_uri = substr($request_uri, strlen('/js/'));
	$file_mode = 'js';
} else {
	$request_uri = substr($request_uri, strlen('/cdn/'));
	if (preg_match('#\.js#', $request_uri) || isset($_GET['m']) && $_GET['m'] == 'js') {
		$file_mode = 'js';
	} else if (preg_match('#\.css#', $request_uri) || isset($_GET['m']) && $_GET['m'] == 'css') {
		$file_mode = 'css';
	}
}

# format
# cdnjs:/twitter-bootstrap/5.0.0-alpha1/js/bootstrap.min.js;
# jsdelivr:/npm/package@version/file;/gh/user/repo@version/file
#


$prefix = [
	'cdnjs'		=>	'https://cdnjs.cloudflare.com/ajax/libs',
	'jsdelivr'	=>	'https://cdn.jsdelivr.net',
	'unpkg'		=>	'https://unpkg.com',
];

$split = explode(';', $request_uri);

# cdnjs by default
$vendor = 'cdnjs';

$urls = [];
foreach ($split as $line) {
	if (empty($line)) continue;

	if (strpos($line, ':')) {
		list($vendor, $suffix) = explode(':', $line);
	} else {
		$suffix = $line;
	}


	if (isset($prefix[$vendor])) {
		$urls[] = $prefix[$vendor] . '/' . ltrim($suffix, '/');
	}
}


header("Pragma: cache");
header("Cache-Control: public, max-age={$ttl}");
header('Access-Control-Allow-Origin: *');

$response = '';
if (!empty($urls)) {
	$urls = array_unique($urls);
	$urls = array_slice($urls, 0, $max_resource);
	$response = '';

	foreach ($urls as $url) {
		header('X-proxy-url: ' . $url, false);
		if ($file_mode == 'js' || $file_mode == 'css') {
			$response .= "/* {$url} */\n\n";
		}
		
		$resource_response = http_get($url);
		$response .= process_file($resource_response, $file_mode, $url);
		$response .= "\n";
	}

	if ($file_mode == 'css') {
		header('content-type: text/css');
	} else if ($file_mode == 'js') {
		header('content-type: application/javascript');
	}

	echo $response;
}


function http_get($url)
{
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
	curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36');
	curl_setopt($ch, CURLOPT_URL, $url);
	$response = curl_exec($ch);
	$info = curl_getinfo($ch);
	return $response;
}

function process_file($content, $file_mode, $url)
{
	if ($file_mode == 'css') {
		$content = process_css($content, $url);
	}
	return $content;
}

function process_css($content, $url)
{
	$url_prefix = dirname($url);
	$content = preg_replace_callback('#url\s*\(\s*(\'|")?(.......)#si', function($matches) use($url_prefix) {
		$object = $matches[2];
		if (preg_match('#^https?:#', $object)) {
			$prefixed = $object;
		} else if (preg_match('#^/#', $object)) {
			# find prefix
			$prefixed = $url_prefix . $object;
		} else {
			# prefix + '/'  + object
			$prefixed = $url_prefix . '/' . $object;
		}
		return 'url(' . $matches[1] . $prefixed;
	}, $content);


	$content = preg_replace_callback('#sourceMappingURL=(......)#is', function($matches) use($url_prefix) {
		if (preg_match('#^https?:#', $matches[1])) {
			return 'sourceMappingURL=' . $matches[1];
		} else {
			return 'sourceMappingURL=' . $url_prefix . '/' . $matches[1];
		}
	}, $content);

	return $content;
}