The chapters in this section of the book, Chapters 8 through 14, are a functional reference. They describe how each PHP function works: what arguments are expected, what value is returned, and how they ought to be used. The functions are grouped generally by what they do.
Chapter 8 is concerned with communication with the browser. In addition to printing text, this chapter covers pregenerated variables and HTTP headers.
Chapter 9 discusses interaction with the operating system, including the local filesystem. There are functions for running other programs, functions for reading and writing files, and a collection of functions to help you debug your scripts.
Chapter 10 describes networking functions. There are functions for generalized network I/O and specialized groups of functions for FTP, HTTP and SNMP transfers.
Chapter 11 is all about data structures. There are functions for handling arrays, objects, and your own functions.
Chapter 12 is concerned with transforming strings. This includes cutting strings into pieces, making hash keys, and executing regular expressions.
Chapter 13 is concerned with mathematics. Aside from the standard mathematical functions you expect, PHP offers some unique features for handling arbitrarily large or small numbers.
Chapter 14 describes time and date functions, including support of alternative calendars.
Chapter 15 discusses configuration of PHP. It lists configuration directives and the functions used to manipulate them.
Chapter 16 is a chapter on graphics functions. The GD library allows you to create and manipulate images on the fly.
Chapter 17 describes the most popular database extensions. This includes MySQL and PostgreSQL.
Chapter 18 is concerned with object layers: COM, CORBA, and Java.
Chapter 19 contains miscellaneous functions, most of which interface with specialized libraries, such as functions for communicating with IMAP and mnoGoSearch servers.
Chapter 20 discusses XML functions.
Throughout this section I've used a standard format for showing how a function works. Each description begins with a prototype for the function. This tells you what type of data the function returns and what type of data is expected to be passed. When a function returns nothing, it isn't preceded with a datatype. Likewise, if a function takes no arguments, the parentheses following the function's name are empty.
Following the prototype is a description of the function. If arguments are optional, it's noted. If an argument needs to be passed by reference, it is noted here. If the function is related to another function, it is referred to here as well.
For most functions, after the description, an example appears. It gives you an idea of how the function might work in a real script. In many cases I've come up with pieces of code that could be dropped into your own script unaltered. Occasionally, I'll point you to another example in the same section where I've grouped several functions in one clear example. Most of the database functions, for example, make little sense outside the context of a complete script.
