As the title suggests, I'm wondering If it's technically possible for a PHP script to act as an SOCKS proxy. If not what are the technical limitations?
I have access to a paid hosting which provides me with executing PHP scripts and a domain name is connected to the host. (e.g. example.com).
Is there any SOCKS proxy written in PHP so I may upload it a directory at host (e.g. example.com/proxy) and configure a client (like Firefox) to connect via the proxy.
What you describe will not work. While PHP does have the ability to create a TCP server, a proxy server in particular must already be running and listening for connections before a client tries to connect to it, and hosting providers execute a PHP script only on an as-needed basis whenever a client requests the script via the HTTP/S protocol, running the script only for the duration of that request. For what you want, you need a dedicated server running your PHP application separate from a web server. You won't get that with a hosting provider.