The following fields are required to be added in the style.css headerHeader The header of your site is typically the first thing people will experience. The masthead or header art located across the top of your page is part of the look and feel of your website. It can influence a visitor’s opinion about your content and you/ your organization’s brand. It may also look different on different screen sizes.:

• Tested up to – the version of WordPress that the theme has been tested against. This should be numbers only, so ‘5.0’ and not ‘WP 5.0’;
• Requires PHP – this field states the lowest version of PHPPHP PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. http://php.net/manual/en/intro-whatis.php. that the theme can utilize. If empty, it will default to whatever the oldest version of PHP that WordPress supports.