DocumentHandler::isNeedConvertExtension

static function isNeedConvertExtension($extension)
{
	static $convertFormat = array(
		'doc' => 'docx',
		'.doc' => '.docx',
		'xls' => 'xlsx',
		'.xls' => '.xlsx',
		'ppt' => 'pptx',
		'.ppt' => '.pptx',
	);

	return isset($convertFormat[$extension]) || isset($convertFormat[mb_strtolower($extension)]);
}