core-bundle/src/Resources/contao/library/Contao/Validator.php
public static function isValidFileName($strName)
	{
		if ($strName == '')
		{
			return false;
		}

		// Special characters not supported on e.g. Windows
		if (preg_match('@[\\\\/:*?"<>|]@', $strName))
		{
			return false;
		}

		// Invisible control characters or unused code points
		if (preg_match('/[\pC]/u', $strName) !== 0)
		{
			return false;
		}

		// Must not be longer than 255 characters
		if (Utf8::strlen($strName) > 255)
		{
			return false;
		}

		return true;
	}
public static function isValidFileName($strName)
	{
		if ($strName == '')
		{
			return false;
		}

		// Special characters not supported on e.g. Windows
		if (preg_match('@[\\\\/:*?"<>|]@', $strName))
		{
			return false;
		}

		// Invisible control characters or unused code points
		if (preg_match('/[\pC]/u', $strName) !== 0)
		{
			return false;
		}

		// Must not be longer than 255 characters
		if (Utf8::strlen($strName) > 255)
		{
			return false;
		}

		return true;
	}
Valid file name

@param mixed $strName The file name

@return boolean True if the file name is valid