Escaped Mutant for Mutator "CastString": --- Original +++ New @@ @@ /** @throws void */ private function filterHeader(string $header) : string { - return (string) preg_replace(["#(?:(?:(?<!\r)\n)|(?:\r(?!\n))|(?:\r\n(?![ \t])))#", '/[^\\x09\\x0a\\x0d\\x20-\\x7E\\x80-\\xFE]/'], '-', $header); + return preg_replace(["#(?:(?:(?<!\r)\n)|(?:\r(?!\n))|(?:\r\n(?![ \t])))#", '/[^\\x09\\x0a\\x0d\\x20-\\x7E\\x80-\\xFE]/'], '-', $header); } }