$re = '/(https?:\/\/[^?]*\??.*?)([&?]filter_productnaam-leverancier=)(.*)/';
$str = 'https://lampgigant.nl/lampen/hanglampen/?filter_productnaam-leverancier=galileo-pendel-14xg420w-d93cm-wit%2Ccosmo-pendel-led-10wd30cm-3000k-920lm-ch&query_type_productnaam-leverancier=or';
$subst = "\1\3";
$result = preg_replace($re, $subst, $str, 1);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php