Is there any way to include the user agent string along with the request send by PHP Simple HTML DOM Parser?
By looking at the code it should be possible by using context streams, something like:
$context = stream_context_create();
stream_context_set_params($context, array('user_agent' => 'UserAgent/1.0'));
file_get_html('http://www.google.com/', 0, $context);
Alternatively you can also set default value in php.ini.