PHP Document Root, Path and URL detection

<?php

/*
 * This snippet was originally written in Sébastien Lavoie's blog.
 * You can find the post at
 * http://blog.lavoie.sl/2013/02/php-document-root-path-and-url-detection.html
 */


$baseDir = __DIR__;
$docRoot = preg_replace( "!{$_SERVER['SCRIPT_NAME']}$!", '', $_SERVER['SCRIPT_FILENAME'] );
$baseUrl = preg_replace( "!^{$docRoot}!", '', $baseDir );
$protocol = empty( $_SERVER['HTTPS'] ) ? 'http' : 'https';
$port = $_SERVER['SERVER_PORT'];
$dispPort = ( $protocol == 'http' && $port == 80 || $protocol == 'https' && $port == 443 ) ? '' : ":$port";
$domain = $_SERVER['SERVER_NAME'];
$fullUrl = "$protocol://{$domain}{$dispPort}{$baseUrl}";