for that you need to use the $_SERVER['PHP_SELF'] variable instead of the $_GET.
$_SERVER['PHP_SELF'] will return the name of the page script:
/services.php
or:
/management.php
<li class="home<?php if(in_array("management.php", explode("/",$_SERVER['PHP_SELF']))) echo(" current"); ?>"><a href="management.php"></li>
<li class="services<?php if(in_array("services.php", explode("/",$_SERVER['PHP_SELF']))) echo(" current"); ?>"><a href="services.php"></li>