Are there specific configurations or settings in PHP that could be causing the issue with umlaut characters in the search?

The issue with umlaut characters in the search could be caused by the character encoding settings in PHP. To solve this issue, you can set the appropriate character encoding in your PHP script using the `mb_internal_encoding()` function. This function sets the internal character encoding to the specified encoding, which can help with handling umlaut characters correctly.

<?php
mb_internal_encoding('UTF-8');
// Your PHP code for handling umlaut characters in the search
?>