Add class="active" to active page using PHP

Question

Dynamic Header, CSS Class Change To Active USING PHP (dirrectory)

I want the class of the <li> tag to change under the active dirrectory... now, every guide shows me how to do it when your page equals it, but i want to change the <li> depending on what dirrectory im on

for example:

if say im on
http://example.com/RESOURCES/code/opensource,
or
http://example.com/RESOURCES/images/clipart
i want the "RESOURCES" ^^ <li> to be 'class="active"' while the rest display 'class="noactive"'

or if im on
http://example.com/tutorials/css/flawless-dropdown-menu
I want the "tutorials" <li> to be 'class="active"' while the rest are 'class="noactive"'

---

URL Setup:

This is my example of how my url's are displayed...

http://example.com/tutorials/css/flawless-dropdown-menu

^^That URL is the page of a tutorial....under the "tutorials" directory, than under the "CSS" category directory, than the page title (all of these directories are not real and are rewrites from .htaccess) [irrelevant]

---

Navigation Setup:

<ul id="mainnav">
  <li class="noactive"><a href="/">Home</a></li>
  <li class="active"><a href="/tutorials/">Tutorials</a></li>
  <li class="noactive"><a href="/resources/">Resources</a></li>
  <li class="noactive"><a href="/library/">Library</a></li>
  <li class="noactive"><a href="/our-projects/">Our Projects</a></li>
  <li class="noactive"><a href="/community/">Community</a></li>
</ul>

Answer 1

Figured out the ANSWER...I was over thinking it.

HTML

<ul id="mainnav">
    <li class="<?php if ($first_part=="") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Home</a></li>
    <li class="<?php if ($first_part=="tutorials") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Tutorials</a></li>
    <li class="<?php if ($first_part=="resources") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Resources</a></li>
    <li class="<?php if ($first_part=="library") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Library</a></li>
    <li class="<?php if ($first_part=="our-projects") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Our Projects</a></li>
    <li class="<?php if ($first_part=="community") {echo "active"; } else  {echo "noactive";}?>"><a href="#">Community</a></li>
</ul>

PHP

<?php 
$directoryURI = $_SERVER['REQUEST_URI'];
$path = parse_url($directoryURI, PHP_URL_PATH);
$components = explode('/', $path);
$first_part = $components[1];
?>

Answer 2

header.php

$activePage = basename($_SERVER['PHP_SELF'], ".php");

nav.php

<ul>
    <li class="<?= ($activePage == 'index') ? 'active':''; ?>"><a href="/index.php">Home</a></li>
    <li class="<?= ($activePage == 'tutorials') ? 'active':''; ?>"><a href="/tutorials.php">Tutorials</a></li>
...