When uploading a large file via the Media uploader, I get the infamous HTTP Error problem. I also have the following in the Chrome console:
POST http://www.nameofsite.co/wp-admin/async-upload.php 500 (Internal Server Error)
The file is actually uploaded and appears in the uploads directory. I have tried all suggestions in the question linked above.
WordPress version is 4.0.1 on 1&1 UK shared hosting
With all plugins disabled, the error does not happen. If I enable, for example, revolution slider, the error occurs. However, I believe more than one plugin or a combination of plugins might be causing the problem. The fact that I am able to upload large images with all plugins disabled leads me to believe that a function or functions within certain plugins is interfering with async upload and that this is not a server config issue.
Other plugins causing the issue – uploadcare, fusion-core
Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.
It’s a bit of a shot in the dark, but would you like to move up your memory limit? My guess is that your uploader fails on uploading big files with more serious plugins on just because they are using some of the memory too. In some cases “Memory exhausted” message does not appear if you don’t have the right server settings.
In any case you should have a verbose error message somewhere in the web server logs, as 500 means exactly this: “There is an error on the server side and I’m not showing it to you, visitor!”.
If you have upgraded the PHP version. This might cause the old plugin to do so. Same thing happened with me. I upgraded php 5.6 to PHP 7 and same error had occur. When i reinstall the PHP 5.6 it started to work normally.