As I wrote in my PHP multithreading with cURL article, the libcurl is a free and easy-to-use client-side URL transfer library, supporting DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP. PHP supports the libcurl library which allows you to connect and communicate to many different types of servers with many different types of protocols.

The tutorial focuses on two different types of connections (well, four really) - FTP/FTPS and HTTP/HTTPS - and how to transfer data across each. Some code is included to create a (procedural) tool to send an uploaded file to a remote site.