A Very Simple PHP Router

Router.php

<?php

class Router 
{
	protected $_routes;

	protected $routeMethods = ['get', 'post'];

	public function add($pattern, $callback, $options) {
		$pattern = '/' . trim($pattern, '/');

		$routerName = isset($options['name']) ? $options['name']: null;

		$type = isset($options['type']) ? strtolower($options['type']) : 'get';

		if(!in_array($type, $this->routeMethods)) {
			throw new InvalidRequestMethodException("'{$type}' isn't a valid request type.");	
		}

		$this->_routes[] = [
			'pretty'	=> $pattern, //The pretty dev-readable version of the route pattern eg : /users/{username}
			'route'		=> $this->parseRoute($pattern), //The actual regex route pattern
			'type'		=> $type, //the request method/type
			'callback' 	=> $callback, //the callback to be run if the route matches
			'name' 		=> $routerName, //the route name to be used in generateRoute()
			];
		}

		// Replaces the pretty placeholders with ugly regex
		public function parseRoute($pattern) {

			// Replace optional paramters eg( get('/users/{username}?') )
			$pattern = preg_replace("/\/{[a-z]+}\?/", "(?:\/([a-zA-Z0-9-_.]*))?", $pattern);

			// Replace required parameters eg( get('/articles/{slug}') )
			$pattern = preg_replace("/{[a-z]+}/", '([a-zA-Z0-9-_.]*)', $pattern);

			return $pattern;
		}

		public function run() {
			$url = isset($_GET['url']) ? '/' . trim(trim($_GET['url']), '/'): '/';

			foreach($this->_routes as $route) {

				//check if the route pattern matches the url
				if(!preg_match("#^{$route['route']}$#", $url, $params)) {
					continue;
				}

				// check if the request is matching
				if(!$this->checkRouteMethod($route['type'])) {
					continue;
				}

				array_shift($params);

				if(is_callable($route['callback'])) {
				//calls the found route callback with the matched parameters
					return call_user_func_array($route['callback'], $params);
				}

				return new \Exception("Route callback isn't an instance of callable.");
			}

		// no routes matched

			header($_SERVER["SERVER_PROTOCOL"]." 404 Not Found", true, 404);
			die('<h1>404 - Page Not Found</h1>');
		}


		// checks if the current request matches a routes required request type
		public function checkRouteMethod($type) {
			$requestType = strtolower($_SERVER['REQUEST_METHOD']);
			
			if(strtolower($type) == $requestType) {
				return true;
			}

			return false;
		}


		// finds a route by its name
		public function searchRoute($name) {
			foreach($this->_routes as $route) {
				if($route['name'] == $name) {
					return $route;
				}
			}

			return false;
		}

		// turns a route pattern into a uri with the given params (if any)
		public function generateRoute($routeName, $params = []) {
			$route = $this->searchRoute($routeName)['pretty'];

			if($params) {
				foreach($params as $name => $value) {
					$route = preg_replace("/{{$name}}\??/", $this->ceoEncode($value), $route);
				}
			}

			return $route;
		}
		
		// The following function was taken from a StackOverFlow post but I edited it.
		public function ceoEncode($string) {
			if(is_array($string)) {
				$encoded = [];
				foreach($string as $key => $value) {
					$encoded[$key] = $this->ceoEncode($value);
				}
				return $encoded;
			}
			
			//Clean up multiple dashes or whitespaces
			$string = preg_replace("/[\s-]+/", " ", $string);
			//Convert whitespaces to dash
			$string = preg_replace("/[\s]/", "-", $string);
			
			return $string;
		}
	}

NOTE: This an example of a router class and it isn't efficient, DON'T use that in a real world example ;)