- var_dump: documentation ( source)
- filter_var: documentation ( source)
<?php
$url='https://www.dropbox.com/s/t16e9t2dyv2snl2/Vind%20gratis%20artikelen%20en%20de%20beste%20koopjes%20op%20nl.pepper.com.pdf';
$valid = filter_var($url,FILTER_VALIDATE_URL) !== false;
var_dump($valid);