What are the potential issues with using special characters, spaces, and umlauts in file names in PHP scripts?

Special characters, spaces, and umlauts in file names can cause issues when handling files in PHP scripts because they can lead to unexpected behavior or errors. To avoid these problems, it is recommended to sanitize file names by removing or replacing these special characters with alphanumeric characters or underscores.

$filename = "file_with_special_chars.txt";
$clean_filename = preg_replace('/[^\w\-\.]/', '_', $filename);
echo $clean_filename;