Chapter 7. I/O AND DISK ACCESS

HTTP Connections............................................................................................

Writing to the Browser...................................................................................

Output Buffering...............................................................................................

Environment Variables...................................................................................

Getting Input from Forms.............................................................................

Cookies

File Uploads

PUT Method Requests

Reading and Writing to Files

Sessions

The include and require Functions

Ultimately, in order to be useful, a script must communicate with the outside world.
We've seen PHP scripts that send text to the browser and get some information from
functions like date. In this chapter we will examine all the ways a PHP script can
exchange data without using special interfaces. This includes reading from local disk
drives, connecting to remote machines on the Internet, and receiving form input.

PHP is similar to other programming environments—with one notable exception: User
input generally comes from HTML forms. The fields in forms are turned into variables.
You can't stop your script in the middle and ask the user a question. This situation
provides unique challenges. Each time a script runs, it is devoid of context. It is not aware
of what has gone on before unless you make it so.

HTTP Connections

It will be helpful to review how data travels between a browser and a Web server. I will
review it simply for purposes of illustration, but you may wish to refer to detailed
descriptions, such as those found on the W3C Web site
http://www.w3.org/Protocols/.

When you type a URL into the location box on your browser, the first task of the browser
is to break it up into important parts, the first of which is the protocol, HTTP. Next is the