PHP Shell - Tool to Execute Arbitrary Shell Commands From Web Browser

PHP Shell is a tool you can use to execute arbitrary shell-commands or browse the filesystem on your remote web server. This replaces, to a degree, a normal telnet connection, and to a lesser degree a SSH connection.

You use it for administration and maintenance of your website, which is often much easier to do if you can work directly on the server. For example, you could use PHP Shell to unpack and move big files around. All the normal command line programs like ps, free, du, df, etc… can be used.