how does this site work?

[dreami0]

How does site like freephptest.com work? do i need additional software to allow users run peace of their php code? and how safe it is?

Thank you.

[Jason]

They are running a locked down version of PHP which allows them to accept public PHP. It then works like any other site.

Example... typing in getcwd() which should show the directory the script is in returns an error. I wouldn't recommend making something like this without knowing the implications.