How can URLs in the form index.php/irgentwas be implemented in PHP?

To implement URLs in the form index.php/irgentwas in PHP, you can use Apache's mod_rewrite module to rewrite the URLs. This involves creating an .htaccess file in the root directory of your website and specifying rewrite rules to redirect requests to the appropriate PHP script.

```php
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php/(.*)$ index.php?url=$1 [L]
```

This code snippet should be placed in an .htaccess file in the root directory of your website. It will rewrite URLs in the form index.php/irgentwas to index.php?url=irgentwas.