The problem seems to be with Apache configuration. Please check your httpd.conf file and check also if any virtual hosts (v-hosts) are defined. More details on the httpd.conf file: http://httpd.apache.org/docs/2.2/configuring.html
WP plugins are meant to be loaded in context of WordPress core load. They won’t work as vanilla PHP, unless you purposely abstract some parts completely away from WordPress. The typical practice is to have actual working WP installation locally and develop in its context.
Force relative path in media library for LAN deployment
Shot in the dark here: have you tried to add /index.php to the end of the URL for the page, e.g. hit http://127.0.0.1:80/wp-admin/index.php instead of just http://127.0.0.1:80/wp-admin/ Not necessarily a solution, but might narrow down the problem a bit if this fixes it for you.
Some things to check: Have you update the site URL in the wp_options table? Once you log-in to wp-admin change the permalink structure and click save – this makes the system refresh all the links. I personally always use MySQL Workbench to Export and Import data for MySQL databases as it makes life much easier.
You’re going to have to edit your functions.php file and add a few lines. This article has a better explanation. I suggest you try here if you haven’t already. https://css-tricks.com/snippets/wordpress/allow-svg-through-wordpress-media-uploader/
Generally speaking, on a local development environment I wouldn’t rely on FTP as an update solution. Fortunately your issue isn’t specific to XAMPP or Apache, but rather a question of server permissions in general. This is good news because it means the following WordPress documentation for Automatic Updates may contain some useful information for you. … Read more
Write Error in WordPress
What version of PHP are you using? This may be a problem with a lower version of PHP. Check your database user for privileges. Also check the php.ini file for max_execution_time, if might be at default value of 30, increase its value to 90 or more and then try again. Hope it helps.
When developing a theme, you should turn on WP_DEBUG in wp-config.php. It will tell you what the error is. For your case, it seems a syntax problem which leads to server down, not an apache issue.