[php] Warning: require_once(): http:// wrapper is disabled in the server configuration by allow_url_include=0

The warning is generated because you are using a full URL for the file that you are including. This is NOT the right way because this way you are going to get some HTML from the webserver. Use:

require_once('../web/a.php');

so that webserver could EXECUTE the script and deliver its output, instead of just serving up the source code (your current case which leads to the warning).