This one is pretty simple but I found it to be pretty useful for editing certain things on the website without having to edit every page like the navbar. For that I found that I can simply write the code for certain objects in a seperate html/php file and use the include function from php to insert that code.
So I'm writing the code for example the navbar into one file:
<div class="navbar">
<ul>
<li><a href="index.php">Home</a></li>
<li><a href="art.php">My Art</a></li>
<li><a href="highvoltage.php">High Voltage</a></li>
<li><a href="random.php">Random things</a></li>
<li><a href="http://clenonserver.de:8080/">Filebrowser</a></li>
</ul>
</div>
And then just put a single line of php code into each page to inlude that file:
include "navbar.php"
Now I can just edit the file for the navbar and it'll be applied on all other pages so I won't have to edit them individually anymore. Although I'm sure there is a better/proper way to do this.