Specifications

Advanced PHP Techniques

ART IV

370

In this chapter, we’ll look at the network-oriented functions in PHP that enable your scripts to

interact with the rest of the Internet. There’s a world of resources out there, and a wide variety

of protocols available for using them. In this section we’ll consider

• An overview of available protocols

• Sending and reading email

• Using other Web services via HTTP

• Using network lookup functions

• Using FTP

• Using generic network communications with cURL

Overview of Protocols

Protocols are the rules of communication for a given situation. For example, you know the pro-

tocol when meeting another person: You say hello, shake hands, communicate for a while, and

then say goodbye. Computer networking protocols are similar.

Like human protocols, different computer protocols are used for different situations and appli-

cations. We use HTTP, the Hypertext Transfer Protocol, for sending and receiving Web pages.

You will probably also have used FTP, file transfer protocol, for transferring files between

machines on a network. There are many others.

Protocols, and other Internet Standards, are described in documents called RFCs, or Requests

for Comments. These protocols are defined by the Internet Engineering Task Force (IETF). The

RFCs are widely available on the Internet. The base source is the RFC Editor at

http://www.rfc-editor.org/

If you have problems when working with a given protocol, the RFCs are the authoritative

source and are often useful for troubleshooting your code. They are, however, very detailed,

and often run to hundreds of pages.

Some examples of well-known RFCs are RFC2616, which describes the HTTP/1.1 protocol,

and RFC822, which describes the format of Internet email messages.

In this chapter, we will look at aspects of PHP that use some of these protocols. Specifically,

we will talk about sending mail with SMTP, reading mail with POP and IMAP, connecting to

other Web servers via HTTP and HTTPS, and transferring files with FTP.

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