Invoice.pdf Umlautausgabe

public function makeValidFileName($sFilename)
{
$sFilename = preg_replace(‘/[s]+/’, ‘_’, $sFilename);
$sFilename = preg_replace(‘/[^a-zA-Z0-9_.-äöüÄÜÖß]/’, ”, $sFilename);
return str_replace(‘ ‘, ‘_’, $sFilename);
}