Very simple router

router.php

<?php

/**
 * Route
 *
 * @param string $method
 * @param string $path
 * @param callable|array $callback
 * @return void
 */
function route(string $method, string $path, ...$callbacks)
{
	// check request method
	if ($_SERVER['REQUEST_METHOD'] !== strtoupper($method)) {
		return;
	}

	// normalize urls
	$path = trim($path, '/');
	$reqUrl = trim(explode('?', $_SERVER['REQUEST_URI'])[0], '/');
	$routeParams = explode('/', $path);

	$indexes = [];
	$pattern = '';
	// iter through every slash and create patterm
	foreach ($routeParams as $index => $param) {
		if ($param[0] == ':') {
			$indexes[substr($param, 1)] = $index;
			$pattern .= '[a-zA-Z0-9]?\/';
			continue;
		}

		$pattern .= "$param\/";
	}

	// finish pattern
	$pattern = "/^" . trim($pattern, '\/') . "\$/";

	if (!preg_match($pattern, $reqUrl)) {
		return;
	}

	$reqParams = explode('/', $reqUrl);

	// match variable parameters
	$params = [];
	foreach ($indexes as $key => $index) {
		$params[$key] = $reqParams[$index];
	}

	// execute callbacks
	foreach ($callbacks as $callback) {
		if (is_callable($callback)) {
			// call closure
			$callback($params);
		} elseif (is_array($callback)) {
			// call class method
			\call_user_func_array($callback, [$params]);
		}
	}
	die;
}

// call with closure
route('GET', '/user', function () {
	// die('user');
	echo 'user';
});

class Controller {
	public static function userDetail($params) {
		echo 'user: ' . $params['userId'];
	}

	public function posts($params) {
		echo 'user: ' . $params['userId'] . '\'s posts';
	}
}

function checkUser($params) {
	if ($params['userId'] != 1) {
		die('Not allowed');
	}
}

// call with user_func
route('GET', '/user/:userId', 'checkUser', [Controller::class, 'userDetail']);
route('GET', '/user/:userId/posts', 'checkUser', [new Controller(), 'posts']);
die('404');