Programming PHP

Declaring a Class

To design your program or code library in an object-oriented fashion, you’ll need to define your own classes, using the class keyword. A class definition includes the class name and the properties and methods of the class. Class names are case-insensitive and must conform to the rules for PHP identifiers. The class name stdClass is reserved. Here’s the syntax for a class definition:

class classname [ extends baseclass ]
{
    [ var $property [ = value ]; ... ]

    [ function functionname (args) {
          // code 
      }
      ...
    ]
}

Declaring Methods

A method is a function defined inside a class. Although PHP imposes no special restrictions, most methods act only on data within the object in which the method resides. Method names beginning with two underscores (__) may be used in the future by PHP (and are currently used for the object serialization methods _ _sleep( ) and _ _wakeup( ), described later in this chapter), so it’s recommended that you do not begin your method names with this sequence.

Within a method, the $this variable contains a reference to the object on which the method was called. For instance, if you call $rasmus->birthday( ), inside the birthday( ) method, $this holds the same value as $rasmus. Methods use the $this variable to access the properties of the current object and to call other methods on that object.

Here’s a simple class definition of the Person class that shows the $this variable in action:

class Person { var $name; function get_name ( ) { return ...