baseurl_guess.php

<?php 

function base_url() {
	$isSecure = false;
	if (isset($_SERVER['HTTPS'])) {
	    $isSecure = $_SERVER['HTTPS'] == 'on';
	} elseif (!empty($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https' || !empty($_SERVER['HTTP_X_FORWARDED_SSL']) && $_SERVER['HTTP_X_FORWARDED_SSL'] == 'on') {
	    $isSecure = true;
	}
	$REQUEST_PROTOCOL = $isSecure ? 'https' : 'http';
	return sprintf("%s://%s", $REQUEST_PROTOCOL, $_SERVER['HTTP_HOST']);
}

// echo base_url();