Support for FTP has been built into PHP since version 3.0.13.
FTP support is not enabled by default on a *nix operating system. To enable it, PHP must be built using the –enable-ftp configure flag. FTP support is already enabled in the binary version of PHP for Windows.
Detailed technical information on the FTP protocol is available at: ftp://ftp.isi.edu/in-notes/rfc959.txt. For a more general overview of FTP, see the documentation included with FTP client and server applications. Users of *nix operating systems can try the following commands:
man ftp
man ftpd