file_get_contents very slow

I am working with a script (that I did not create originally) that generates a pdf file from an HTML page. The problem is that it is now taking a very long time, like 1-2 minutes, to process. Supposedly this was working fine originally, but has slowed down within the past couple of weeks.

The script calls file_get_contents on a php script, which then outputs the result into an HTML file on the server, and runs the pdf generator app on that file.

I seem to have narrowed down the problem to the file_get_contents call on a full url, rather than a local path.

When I use

$content = file_get_contents('test.txt');

it processes almost instantaneously. However, if I use the full url

$content = file_get_contents('http://example.com/test.txt');

it takes anywhere from 30-90 seconds to process.

It’s not limited to our server, it is slow when accessing any external url, such as http://www.google.com. I believe the script calls the full url because there are query string variables that are necessary that don’t work if you call the file locally.

I also tried fopen, readfile, and curl, and they were all similarly slow. Any ideas on where to look to fix this?