Thank you very much for your script, this is exactly what I was looking for!
However, I have a few problems with it:
To get it to run, I first had to save the PHP file in your post as index.php in the /tmp directory of my webserver. I had to read the source code to know that, it would be nice to have it in the documentation.
I tested it with several proxylists from today, combined about 4500 unique proxy
ort combinations. In my access logfiles of the webserver I saw that more than 1200 of them successfully retrieved the /tmp/index.php testscript. But the proxyc script just terminates after the last process finished, without printing any results on the screen. Where do I get the results?