How to get base url and go back facility in php

How to get base url and go back facility in php

Here for very normal code for that 

just get base url then you can try this code

<?php echo "http://" . $_SERVER['SERVER_NAME'] . 

$_SERVER['REQUEST_URI']; ?>

try i think it's working for you and you want create go back

<a href="#" onclick="window.history.back();">Go Back

this two for php very usefull check it suggest me.