$re = '/.*\/(infografik-kategorien)\/(.*)\/(?!.*term).*/m';
$str = 'https://test.ixtract.de/infografik-kategorien/prozess/';
$subst = "https://test.ixtract.de/Infografik-kategorien/$2/?term=$2";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$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