PHP - 如何更改链接的类

I am trying to learn PHP for a website that I am building. In CSS, I have a class, nav a.thispage, setup to make a 'button' on the navigation be the same color as the highlight. It works beautifully. But, as I added pages, I find that I needed to constantly update all of the HTML files of the site, over, and over again. I found out that PHP could help me to automate this. I use the following PHP, in my HTML to do this:

 <?php include 'content/header.php';?>

The header.php file has the following content:

<header>
  <h1><img id="headerimage" src="Images/GrandLodge.png"/>Lodge</h1>
  <nav>
    <ul>
      <li><a href="index.php">Home</a></li>
      <li><a href="events.php">Events</a></li>
      <li><a href="social.php">Social</a></li>
      <li><a href="about.php">About</a></li>
      <li><a href="contact.php">Contact</a></li>
      <li><a href="gamestores.php">Area Game Stores</a></li>
      <li><a href="http://someaddress" target="_blank">PFS</a></li>
    </ul>
  </nav>
</header>

Now, because I am using this method, I can't just set the class="thispage" on the a tag. Is there a way to set the class, dynamically, with PHP? If so, how to I tell if the page loading the html is actually the page that needs it? Is using PHP even the correct way to handle this, or should I be using JavaScript?

I know this is a lot, and I didn't really provide a lot of what I have done, but I can't actually seem to see what I need to do for this. All I really need is a point in the right direction, rather than a full code sample.

Thank you for any help you can provide.

You can use a bit oF PHP and JavaScript to handle this

<header>
   <h1><img id="headerimage" src="Images/GrandLodge.png"/>Lodge</h1>
   <nav>
     <ul>
       <li><a id="aHome" href="index.php">Home</a></li>
       <li><a id="aEvents" href="events.php">Events</a></li>
       <li><a id="aSocial" href="social.php">Social</a></li>
       <li><a id="aAbout" href="about.php">About</a></li>
       <li><a id="aContact" href="contact.php">Contact</a></li>
       <li><a id="aGame" href="gamestores.php">Area Game Stores</a></li>
       <li><a id="aPFS" href="http://someaddress" target="_blank">PFS</a></li>
     </ul>
   </nav>
 </header>

Now suppose the visitor has landed on the About page. The code to check that and set the class name on the a tag would be

 <?php
    if ($_SERVER['SCRIPT_NAME'] == '/about.php') { 
 ?>
 <script type="text/javascript">
   document.getElementById("aAbout").className = 'thispage';
 </script>
 <?php
   }
 ?>

Try it and let me know.

Use basename($_SERVER['REQUEST_URI'])

    <header>
      <h1><img id="headerimage" src="Images/GrandLodge.png"/>Lodge</h1>
      <nav>
        <ul>
        <?php $basename = basename($_SERVER['REQUEST_URI']);?>
$class = $basename === 'index.php' || empty($basename) ? ' class="thispage"' : '';
          <li <?php if($basename=="index.php" || $basename==""){?> class="thispage" <?php } ?>><a href="index.php">Home</a></li>
          <li <?php if($basename=="events.php"){?> class="thispage" <?php } ?>><a href="events.php">Events</a></li>
          <li <?php if($basename=="social.php"){?> class="thispage" <?php } ?>><a href="social.php">Social</a></li>
          <li <?php if($basename=="about.php"){?> class="thispage" <?php } ?>><a href="about.php">About</a></li>
          <li <?php if($basename=="contact.php"){?> class="thispage" <?php } ?>><a href="contact.php">Contact</a></li>
          <li <?php if($basename=="gamestores.php"){?> class="thispage" <?php } ?>><a href="gamestores.php">Area Game Stores</a></li>
          <li><a href="http://someaddress" target="_blank">PFS</a></li>
        </ul>
      </nav>
    </header>

Updated another Simple way

<header>
      <h1><img id="headerimage" src="Images/GrandLodge.png"/>Lodge</h1>
      <nav>
        <ul>
        <?php $basename = basename($_SERVER['REQUEST_URI']);?>
         $class = $basename === 'index.php' || empty($basename) ? ' class="thispage"' : '';
          <li <?= $class ?>><a href="index.php">Home</a></li>
          <li <?= $class ?>><a href="events.php">Events</a></li>
          <li <?= $class ?>><a href="social.php">Social</a></li>
          <li <?= $class ?>><a href="about.php">About</a></li>
          <li <?= $class ?>><a href="contact.php">Contact</a></li>
          <li <<?= $class ?>><a href="gamestores.php">Area Game Stores</a></li>
          <li><a href="http://someaddress" target="_blank">PFS</a></li>
        </ul>
      </nav>
    </header

In order for PHP to help you, you'd have to generate your navigation within a loop. Something along the lines of:

<?php 
    $menu = array(
        'Home'   => 'index.php',
        'Events' => 'events.php',
        'Social' => 'social.php',
        'About'  => 'about.php'
    );
?>

<?php foreach ($menu as $name => $href) : ?>
    <?php $class_name = basename(__FILE__) === $href ? 'thispage' : ''; ?>
    <li><a href="<?php echo $href; ?>" class="<?php echo $class_name; ?>"><?php echo $name; ?></a></li>
<?php endforeach; ?>