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

20
Using Network and Protocol
Functions
IN THIS CHAPTER, WE LOOK AT THE NETWORK-ORIENTED functions in PHP that enable
your scripts to interact with the rest of the Internet. A world of resources is available out
there, and a wide variety of protocols is available for using them.
Key topics covered in this chapter include
n Examining available protocols
n Sending and reading email
n Using data from other websites
n Using network lookup functions
n Using FTP
Examining Available Protocols
Protocols are the rules of communication for a given situation. For example, you know
the protocol when meeting another person:You say hello, shake hands, communicate for
a while, and then say goodbye. Different situations require different protocols. Also, people
from other cultures may expect different protocols, which may make interaction difficult.
Computer networking protocols are similar.
Like human protocols, different computer protocols are used for different situations
and applications. For instance, you use the Hypertext Transfer Protocol (HTTP) when
you request and receive web pages—your computer requests a document (such as an
HTML or PHP file) from a web server, and that server responds by sending the document
to your computer. You probably also have used the File Transfer Protocol (FTP)
for transferring files between machines on a network. Many others are available.
Most protocols and other Internet standards are described in documents called
Requests For Comments (RFCs).These protocols are defined by the Internet Engineering