Building An Extensible Form Validator Class - Back To Class (
Page 2 of 12 )
Before we begin, let's just go over the
basics quickly:
In PHP, a "class" is simply a set of program statements
which perform a specific task. A typical class definition contains both
variables and functions, and serves as the template from which to spawn specific
instances of that class.
Once a class has been defined, PHP allows you
to spawn as many instances of the class as you like. These instances of a class
are referred to as "objects". Each of these instances is a completely
independent object, with its own properties and methods, and can thus be
manipulated independently of other objects.
This comes in handy in
situations where you need to spawn more than one instance of an object - for
example, two simultaneous database links for two simultaneous queries, or two
shopping carts. Classes also help you to separate your code into independent
modules, and thereby simplify code maintenance and changes.
A class
definition typically looks like this:
<?php
class ShoppingCart
{
// this is where the properties are defined
var $items;
var $quantities;
var $prices;
...
// this is where the methods are defined
function validate_credit_card()
{
// code goes here
}
...
}
?>
Once the class has been defined, an object can be spawned
with the "new" keyword and assigned to a PHP variable,
<?php
$myCart = new ShoppingCart;
?>
which can then be used to access all object methods and
properties.
<?php
// accessing properties
$myCart->items = array("eye of newt", "tail of lizard", "wings of bat");
$myCart->quantities = array(9, 4, 14);
// accessing methods
$myCart->validate_credit_card();
?>
