PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

452 Chapter 20 Using Network and Protocol Functions
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 documents that define
them are the authoritative sources 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 look at aspects of PHP that use some of these protocols.
Specifically, we discuss sending mail with SMTP, reading mail with POP3 and IMAP4,
connecting to other web servers via HTTP, and transferring files with FTP.
Sending and Reading Email
The main way to send mail in PHP is to use the simple mail() function.We discussed
the use of this function in Chapter 4,“String Manipulation and Regular Expressions,” so
we won’t visit it again here.This function uses the Simple Mail Transfer Protocol
(SMTP) to send mail.
You can use a variety of freely available classes to add to the functionality of mail().
In Chapter 30,“Building a Mailing List Manager,” you use an add-on class to send
HTML attachments with a piece of mail. SMTP is only for sending mail.The Internet
Message Access Protocol (IMAP4), described in RFC2060, and Post Office Protocol
(POP3), described in RFC1939 or STD0053, are used to read mail from a mail server.
These protocols cannot send mail.
IMAP4 is used to read and manipulate mail messages stored on a server and is more
sophisticated than POP3, which is generally used simply to download mail messages to a
client and delete them from the server.
PHP comes with an IMAP4 library. It can also be used to make POP3 and Network
News Transfer Protocol (NNTP) as well as IMAP4 connections.
We look extensively at the use of the IMAP4 library in the project described in
Chapter 29,“Building a Web-Based Email Service.”
Using Data from Other Websites
One of the great things you can do with the Web is use, modify, and embed existing
services and information into your own pages. PHP makes this very easy. Let’s look at an
example to illustrate this use.
Imagine that the company you work for wants the company’s stock quote displayed
on its home page.This information is available on some stock exchange site somewhere,
but how do you get at it?