It is a base URL any web application base on php

php_base_url.php

<?php


function base_url($atRoot = FALSE, $atCore = FALSE, $parse = FALSE)
{
    if (isset($_SERVER['HTTP_HOST'])) {
        $http = isset($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off' ? 'https' : 'http';
        $hostname = $_SERVER['HTTP_HOST'];
        $dir = str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);

        $core = preg_split('@/@', str_replace($_SERVER['DOCUMENT_ROOT'], '', realpath(dirname(__FILE__))), NULL, PREG_SPLIT_NO_EMPTY);
        $core = $core[0];

        $tmplt = $atRoot ? ($atCore ? "%s://%s/%s/" : "%s://%s/") : ($atCore ? "%s://%s/%s/" : "%s://%s%s");
        $end = $atRoot ? ($atCore ? $core : $hostname) : ($atCore ? $core : $dir);
        $base_url = sprintf($tmplt, $http, $hostname, $end);
    } else $base_url = 'http://localhost/';

    if ($parse) {
        $base_url = parse_url($base_url);
        if (isset($base_url['path'])) if ($base_url['path'] == '/') $base_url['path'] = '';
    }

    return $base_url;
}

echo base_url();