When upload a theme to my WordPress hosting, I get this error: "PHP Warning: POST Content-Length of xxx bytes exceeds the limit of 8388608 bytes in Unknown on line 0". This is because you exceeded the limit of uploading files.
In order to solve this problem, you have to edit the
php.ini file in your hosting.
You have find post_max_size and upload_max_filesize, then change the default number to 30M or what ever you want.
After changing your file, restart your web server (for local hosting) or try to upload your file again.