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Web Technologies-I

Notes • PHP gives us a very simple way to define an object programmatically, and this is called
a class.
• A class is a wrapper that defines and encapsulates the object along with all of its methods
and properties.

• A method is essentially a function within a class, and a class may contain no methods, or
thousands of methods. Properties are exactly what they seem to be, they are the properties
of the object, and we usually use methods to set, modify and get properties from an object.
• The data associated with an object are called its properties. The functions associated with
an object are called its methods. When you define a class, you define the names of its
properties and give the code for its methods.

• PHP is not an object-oriented language, it has extensive support for objects. Also, since
PHP 5, many core aspects of the language use objects rather than ordinary (procedural)
functions.
• Classes can be considered as a collection of methods, variables and constants. They often
reflect a real-world thing, like an animal class or a bird class.
• Visibility is a big part of OOP. It allows you to control where your class members can be
accessed from, for instance to prevent a certain variable to be modified from outside the
class.

• Abstract classes are special because they can never be instantiated. Instead, you typically
inherit a set of base functionality from them in a new class. For that reason, they are
commonly used as the base classes in a larger class hierarchy.
• Object introspection is an often overlooked feature in PHP. With the advent of PHP 5
there are all sorts of new additions to the world of PHP object introspection as well.

• Abstract classes are similar in many ways to interfaces. The main difference between
an abstract and an interface is that abstracts allow some control over how the declared
methods are defined.

8.9 Keywords

Abstract class: Abstract class is a class that can not be instantiated, it exists extensively for
inheritance and it must be inherited. There are scenarios in which it is useful to define classes
that are not intended to instantiate; because such classes normally are used as base-classes in
inheritance hierarchies, we call such classes abstract classes.

Class: A class is a template definition of the methods and variables in a particular kind of object.
Constant: A constant is, just like the name implies, a variable that can never be changed.
Constructor: Constructor is a default member function available with a class. It can be explicitly
defined in a class to initialize the variables. Constructor is called when an object is created for
a class.

Destructor: Destructor is special functions which are automatically called when an object is
created and destroyed.

Inheritance: Inheritance is one of the most important aspects of OOP. It allows a class to inherit
members from another class.
Introspection: Object introspection refers to the ability of a class object to reveal information
about itself, such as methods and variables.

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