Fatal error: Uncaught Error: Call to undefined function mysql_connect()
<p>I am trying to do a simple connection with XAMPP and MySQL server, but whenever I try to enter data or connect to the database, I get this error.</p>

<blockquote>
  <p>Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\register.php:22<br>
  Stack trace: #0 {main} thrown in C:\xampp\htdocs\register.php on line 22</p>
</blockquote>

<p>Example of line 22:</p>

<pre><code>$link = mysql_connect($mysql_hostname , $mysql_username);
</code></pre>