Specifications

User-Declared Variables

You can declare and use your own variables in addition to the variables you are passed from

the HTML form.

One of the features of PHP is that it does not require you to declare variables before using

them. A variable will be created when you first assign a value to it—see the next section for

details.

Assigning Values to Variables

You assign values to variables using the assignment operator, =. On Bob’s site, we want to

work out the total number of items ordered and the total amount payable. We can create two

variables to store these numbers. To begin with, we’ll initialize each of these variables to zero.

Add these lines to the bottom of your PHP script:

$totalqty = 0;

$totalamount = 0.00;

Each of these two lines creates a variable and assigns a literal value to it. You can also assign

variable values to variables, for example:

$totalqty = 0;

$totalamount = $totalqty;

Variable Types

A variable’s type refers to the kind of data that is stored in it.

PHP’s Data Types

PHP supports the following data types:

• Integer—Used for whole numbers

• Double—Used for real numbers

• String—Used for strings of characters

• Array—Used to store multiple data items of the same type (see Chapter 3, “Using

Arrays”)

• Object—Used for storing instances of classes (see Chapter 6, “Object Oriented PHP”)

PHP also supports the pdfdoc and pdfinfo types if it has been installed with PDF (Portable

Document Format) support. We will discuss using PDF in PHP in Chapter 29, “Generating

Personalized Documents in Portable Document Format.”

Using PHP

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