Object oreinted php | OOPs

A Presentation by
ADMEC Multimedia Institute & Web Development Institute (WDI) Delhi
Twitter: @admecinstitute
www.admecindia.co.in
www.web-development-institute.com

 The purpose of this PHP presentation is to explain
Object Oriented PHP in brief.
 This PHP presentation can help a PHP programmer
in understanding the terms and terminologies used
in practical object oriented PHP.
 Frameworks of PHP like CodeIgniter, CakePHP,
Symphony, Zend etc are MVC based and knowledge
of Object Oriented PHP will help in understanding
all them.

 Basics of OOP in PHP
 Object & Classes in OOP
 Magic Function in PHP OOP
 Inheritance (Extending a class)
 Visibility (public, private, protected)
 Abstract Classes in PHP
 Static Methods and properties in PHP
 Interfaces in PHP
 Explaining PHP Class Functions
 Describing Autoload in PHP

 PHP is a scripting language
 Specially a Procedural Programming
 Not a true OO Programming
 It supports few OO features
 Full OOP Support added as of PHP5

 It is Object Oriented Programming method of
coding.
 Allow developer to group multiple similar
tasks into classes.
 The main aim of OOP is to not repeat the
similar code again and again.
 With OOP, it is easy to maintain the structure
of application and organizing the data
 OOP provide simplicity to the complex
applications code.

 Code organization and maintainability
 Add clarity
 Reduce complexity
 Simple rules allow complex interactions
 Emphasizes data over procedure
 Code modularity or refactoring
 Code reusability
 Well-suited for databases

 It depends
 My PHP OOP rule of thumb
◦ For a simple site, OOP adds unnecessary complexity
◦ For a complex site, OOP adds necessary simplicity

Concept of classes & objects can be
explained with these two images:
 A class, for example, is like a blueprint for a
house. It defines the shape of the house on
paper, with relationships between the different
parts of the house clearly defined and planned
out, even though the house doesn't exist.
 An object, then, is like the actual house built
according to that blueprint. The data stored in
the object is like the wood, wires, and
concrete that compose the house: without
being assembled according to the blueprint,
it's just a pile of stuff. However, when it all
comes together, it becomes an organized,
useful house.

In PHP class is created using class keyword as shown in the
following example
class myOwnClass
{
//variables of the class
var $variable1;
var $variable2;
//Function of class
function mergeVariable()
{
return $this->variable1 . $this->variable2;
}
}

There is no use of classes without objects. Object is representative
of your class. If created a class then you must need to create object
of the class to solve your problem using class. You can create object
of your class by using new keyword.
$objClass = new myClass();
Now in above code you are creating object of class myClass in
variable $objClass. You can create multiple object of your same
class. Every object is different from other.
$objClass1 = new myClass();
$objClass2 = new myClass();

Magic methods in php are some predefined function by php
compiler which executes on some event. Magic methods starts with
prefix __, for example __call, __get, __set.
List of Magic Functions in PHP
__construct
This magic methods is called when
someone create object of your class.
Usually this is used for creating
constructor in php5.
__destruct
This magic method is called when object
of your class is unset. This is just
opposite of __construct.

__get
This method called when your object
attempt to read property or variable of the
class which is inaccessible or unavailable.
__set
This method called when object of your
class attempts to set value of the property
which is really inaccessible or
unavailable in your class.
__isset
This magic methods trigger when isset()
function is applied on any property of the
class which is inaccessible or unavailable.
__unset
__unset is something opposite of isset
method. This method triggers when
unset() function called on inaccessible or
unavailable property of the class.

__call
__call magic method trigger when you are
attempting to call method or function of
the class which is either inaccessible or
unavailable.
__callstatic
__callstatic execture when inaccessible or
unavailable method is in static context.
__sleep
__sleep methods trigger when you are
going to serialize your class object.
__wakeup
__wakeup executes when you are
un serializing any class object.

There are 3 type of visibility available in PHP for controlling
your property or method.
 Public: Public method or variable can be accessible from
anywhere. I mean from inside the class, out side the class and
in child(will discuss in next chapter) class also.
 Private: Method or property with private visibility can only be
accessible inside the class. You can not access private
method or variable from outside of your class.
 Protected: Method or variable with protected visibility can
only be access in the derived class. Or in other word in child
class. Protected will be used in the process of inheritance.

 The abstract classes and methods are used to create a model
of minimum required methods which must be defined in
normal sub-classes derived from an abstract class (with
extends).
 An abstract class is created with the abstract keyword.
 An abstract class cannot be instantiated, can only be
inherited by other sub-classes extended from it.
 The abstract methods are declared with the abstract keyword,
and cannot have an implementation, they simply declare the
method's signature. abstract public function method
Name($arguments);

In this example is created an abstract class with a property
($name), an abstract method ( greetName() ) and a normal
method ( setName() ).
<?php
// AbstractClass class
abstract class AbstractClass {
protected $name;
// declare an abstract method
abstract public function greetName($greet);
// define a normal method
public function setName($name) {
$this->name = $name; // sets the value of $name property
}
} ?>

 Static methods and properties in php is very useful
feature.
 Static methods and properties in php can directly
accessible without creating object of class.
 Your php class will be static class if your all methods and
properties of the class is static.
 Static Methods and Properties in PHP will be treated as
public if no visibility is defined.
 Static properties of class is a property which is directly
accessible from class with the help of ::(scope resolution
operator). You can declare static property using static
keyword.

 You can define a common structure for your classes using
interfaces.
 An Interface is like a template similar to abstract class
with a difference where it uses only abstract methods.
 In simple words, an interface is like a class using
interface keyword and contains only function
declarations(function with no body).
 An Interface should be implemented in the class and all the
methods or functions should be overridden in this class.
 It is the place where we can define the function.
When a class use that interface in that class the total
function body part will describe.
after that we can call that function in other class and we
are get result.

Example of interface:
 interface InterfaceName{
function fun1();
function fun2(a,b);
}
class ClassName implements InterfaceName{
fuction fun1(){
function implementation.......
}
fuction fun2(a,b){
function implementation.......
}
}

 For abstract class a method must be
declared as abstract. Abstract
methods doesn’t have any
implementation.
 The Abstract methods can declare
with Access modifiers like public,
internal, protected. When
implementing in subclass these
methods must be defined with the
same (or a less restricted) visibility.
 Abstract class can contain variables
and concrete methods.
 A class can Inherit only one Abstract
class and Multiple inheritance is not
possible for Abstract class.
For interface all the methods by default
are abstract methods only. So one cannot
declare variables or concrete methods in
interfaces.
All methods declared in an interface must
be public.
Interfaces cannot contain variables and
concrete methods except constants.
A class can implement many interfaces
and Multiple interface inheritance is
possible.

PHP has available several class functions to help you through the
OOP mine field.
 get_declared_interfaces()
 class_exists()
 get_class()
 get_declared_classes()
 Each of these is shown here beginning with the
get_declared_interfaces().

get_declared_interfaces()
following function provides an array of all the available declared
interfaces.
<?php
interface fax{
public function dial();
public function send();
public function recieve();
}
interface printer{
public function printBlack();
public function printColor();
public function printDraft();
public function kick();
}
/*** our interface implementation ***/
class printerFax implements fax, printer{
public function dial(){ }
public function send(){ }
public function recieve(){ }

public function printBlack(){ }
public function printColor(){ }
public function printDraft(){ }
public function kick(){ }
}
/*** create and printerfax object ***/
$object = new printerFax;
/*** get the declared interfaces ***/
foreach(get_declared_interfaces() as $key=>$interface)
{
echo $key.' => '.$interface.' ';
}
?>

 get_class()
 class_exists()
 get_declared_classes
<?php
/*** a pretend class ***/
class fax{
public function dial(){ }
public function send(){ }
public function recieve(){ }
}
/*** another pretend class ***/
class printer{
public function printBlack(){ }
public function printColor(){ }
public function printDraft(){ }
public function kick(){ }
}

/*** create an instance of the fax class ***/
$foo = new fax;
/*** create an instance of the printer class ***/
$bar = new printer;
echo '$foo is from the ' get_class($foo).' class ';
echo class_exists("printer").' ';
echo 'Declared classes are: ';
foreach(get_declared_classes() as $key=>$classname)
{
echo $key.' -> '.$classname.' ';
}
?>

 Many developers writing object-oriented applications create
one PHP source file per class definition. One of the biggest
annoyances is having to write a long list of needed includes at
the beginning of each script (one for each class).
 In PHP 5, this is no longer necessary. You may define an
__autoload() function which is automatically called in case you
are trying to use a class/interface which hasn't been defined
yet. By calling this function the scripting engine is given a last
chance to load the class before PHP fails with an error.

<?php
/*** include our class definitions ***/
include('classes/vehicle.class.php');
include('classes/motorcycle.class.php');
include('classes/printer.class.php');
include('classes/printer.class.php');
/*** instantiate a new vehicle class object ***/
$vehicle = new vehicle;
*** instantiate a new motorcycle class object ***/
$bike = new motorcycle;
*** instantiate a new printer class object ***/
$printer = new printer;
*** instantiate a new fax class object ***/
$fax = new fax;
?>

With __autoload() the above code can be reduce to following
<?php
/*** Autoload class files ***/
function __autoload($class){
require('classes/' . strtolower($class) . '.class.php');
}
/*** instantiate a new vehicle class object ***/
$vehicle = new vehicle;
/*** instantiate a new motorcycle class object ***/
$bike = new motorcycle;
/*** instantiate a new printer class object ***/
$printer = new printer;
/*** instantiate a new fax class object ***/
$fax = new fax;
?>

ADMEC Multimedia Institute
For more info you can visit
www.admecindia.co.in and www.web-development-institute.com
For course related enquiry, ring us at:
9811-81-81-22, 011-3203-5055
Created by: Parul Sabal
Guided by: Ravi Bhadauria

Object oreinted php | OOPs

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