Object Oreinted PHP | OOPs

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Object Oriented Programming with PHP

• A Presentation byADMEC Multimedia Institute
  Web Development Institute (WDI) Delhi

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PHP Presentations Purpose

• 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.

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Topics to be Covered

• 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

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Concept and Basics of 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

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What is OOP

• 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.

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Why is OOP Useful in PHP?

• 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

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Do You Need OOP?

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

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Classes Objects in PHP

• 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.

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Classes Objects in PHP

• 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 mergeVaria
  ble() return this-gtvariable1 .
  this-gtvariable2

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Classes Objects in PHP

• 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()

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Magic Functions in PHP OOP

• 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.
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Magic Functions in PHP OOP
__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.
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Magic Functions in PHP OOP
__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.
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Inheritance in PHP

• Inheritance is a well-established programming
  principle, and PHP makes use of this principle in
  its object model. This principle will affect the
  way many classes and objects relate to one
  another.
• For example, when you extend a class, the
  subclass inherits all of the public and protected
  methods from the parent class. Unless a class
  overrides those methods, they will retain their
  original functionality.
• This is useful for defining and abstracting
  functionality, and permits the implementation of
  additional functionality in similar objects
  without the need to reimplement all of the shared
  functionality.

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Visibility in PHP

• 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.

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Abstract Classes in PHP

• 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)

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Abstract Classes in PHP

• In this example is created an abstract class with
  a property (name), an abstract method (
  greetName() ) and a normal method ( setName() ).
• lt?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-gtname name // sets the value of
  name property
• ?gt

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Static Methods Properties in PHP

• 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.

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Interfaces in PHP

• You can define a common structure for your
  classes using interfaces.
• An Interface is like a template similar to
  abstract classwith a difference where it uses
  only abstract methods.
• In simple words, an interface is like a class
  usinginterface keyword and contains only
  functiondeclarations(function with no body).
• An Interface should be implemented in the class
  and all themethods 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.

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Interfaces in PHP

• 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.......  

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Differences between an Abstract Class and an
Interface in PHP

• For abstract class a method must be declared as
  abstract. Abstract methods doesnt 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.
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PHP Class Functions in PHP

• 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().

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PHP Class Functions in PHP

• get_declared_interfaces()
• following function provides an array of all the
  available declared interfaces.
• lt?phpinterface fax  public function dial()  p
  ublic function send()  public function recieve()
  interface printer  public function printBla
  ck()  public function printColor()  public fun
  ction printDraft()  public function kick()/
   our interface implementation /class printe
  rFax implements fax, printer  public function di
  al()   public function send()   public funct
  ion recieve() 

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PHP Class Functions in PHP

•   public function printBlack()   public functio
  n printColor()   public function printDraft() 
    public function kick() 
•   / create and printerfax object /  obj
  ect  new printerFax  / get the declared inte
  rfaces /  foreach(get_declared_interfaces() as
   keygtinterface)                echo key.' 
  gt '.interface.'ltbr /gt'        ?gt

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Other Functions in PHP

• get_class()
• class_exists()
• get_declared_classes

lt?php/ a pretend class /class fax  publi
c function dial()   public function send()  
 public function recieve() / another pret
end class /class printer  public function pr
intBlack()   public function printColor()   
public function printDraft()   public function 
kick() 
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Other Functions in PHP

• / create an instance of the fax class /fo
  o  new fax/ create an instance of the print
  er class /bar  new printerecho 'foo is f
  rom the ' get_class(foo).' classltbr /gt'echo cla
  ss_exists("printer").'ltbr /gt'echo 'Declared clas
  ses areltbr /gt 'foreach(get_declared_classes() a
  s keygtclassname)        echo key.' -gt '.
  classname.'ltbr /gt'    ?gt

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Autoload in PHP

• 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.

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Autoload in PHP

• lt?php/ include our class definitions /in
  clude('classes/vehicle.class.php')include('clas
  ses/motorcycle.class.php')include('classes/prin
  ter.class.php')include('classes/printer.class.p
  hp')/ instantiate a new vehicle class object
   /vehicle  new vehicle instantiate a n
  ew motorcycle class object /bike  new motorc
  ycle instantiate a new printer class object 
  /printer  new printer instantiate a ne
  w fax class object /fax  new fax?gt

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Autoload in PHP

• With __autoload() the above code can be reduce to
  following
• lt?php/ Autoload class files /function __a
  utoload(class)  require('classes/' . strtolower
  (class) . '.class.php')/ instantiate a ne
  w vehicle class object /vehicle  new vehicle
  / instantiate a new motorcycle class object 
  /bike  new motorcycle/ instantiate a n
  ew printer class object /printer  new printe
  r/ instantiate a new fax class object /
  fax  new fax?gt

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Created by Parul Sabal Guided by Ravi Bhadauria
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