PHP Classes and OOPS Concept

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To find how to use OOPS Concept in PHP and the Class utilization in PHP latest version

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  • PHP Classes and Object Orientation
  • Revision HIstory # Version Date Rationale for change Change Description 1 1.0 26-Feb-2008 Initial Version 2
  • Revision HIstory Document Name Training Material Document Code QMS-TEM-OT 08 Version 1.0 Date 26-Feb-2008 Created By Ms. Padmavathy Reviewed BY SPG Approved By Mr. Vijay
  • Agenda
    • Introduction
    • Function
    • Class Definition
    • Class Usage
    • Constructor
    • Inheritance
    • PHP4 vs PHP5
  • Reminder a function
    • Reusable piece of code.
    • Has its own local scope.
    • function my_func($arg1,$arg2) {
    • >
    • }
  • Conceptually, what does a function represent? give the function something (arguments), it does something with them, and then returns a result Action or Method
  • What is a class ? Conceptually, a class represents an object , with associated methods and variables
  • Class Definition An example class definition for a dog. The dog object has a single attribute, the name, and can perform the action of barking.
  • Class Definition class dog { Define the name of the class.
  • Class Definition public $name; Define an object attribute (variable), the dogs name.
  • Class Definition public function bark() { echo Woof! ; } Define an object action (function), the dogs bark.
  • Class Defintion Similar to defining a function.. The definition does not do anything by itself . It is a blueprint, or description, of an object. To do something, you need to use the class
  • Class Usage
  • Class Usage require ( dog.class.php ); Include the class definition
  • Class Usage $puppy = new dog(); Create a new instance of the class.
  • Class Usage $puppy->name = Rover ; Set the name variable of this instance to Rover.
  • Class Usage echo {$puppy->name} says ; Use the name variable of this instance in an echo statement..
  • Class Usage $puppy->bark(); Use the dog object bark method.
  • One dollar and one only $puppy->name = Rover ; The most common mistake is to use more than one dollar sign when accessing variables. The following means something entirely different.. $puppy->$name = Rover ;
  • Using attributes within the class..
    • If you need to use the class variables within any class actions, use the special variable $this in the definition:
    • class dog {
    • public $name;
    • public function bark() {
    • echo $this->name. says Woof! ; }
    • }
  • Constructor methods
    • A constructor method is a function that is automatically executed when the class is first instantiated.
    • Create a constructor by including a function within the class definition with the __construct name .
    • Remember.. if the constructor requires arguments, they must be passed when it is instantiated!
  • Constructor Example
  • Constructor Example Constructor arguments are passed during the instantiation of the object.
  • Class Scope
    • Like functions, each instantiated object has its own local scope.
    • e.g. if 2 different dog objects are instantiated, $puppy1 and $puppy2 , the two dog names $puppy1->name and $puppy2->name are entirely independent..
  • Inheritance
    • The real power of using classes is the property of inheritance creating a hierarchy of interlinked classes.
    dog poodle alsatian parent children
  • Inheritance
    • The child classes inherit all the methods and variables of the parent class, and can add extra ones of their own.
    • e.g. the child classes poodle inherits the variable name and method bark from the dog class, and can add extra ones
  • Inheritance example The American Kennel Club (AKC) recognizes three sizes of poodle - Standard, Miniature, and Toy class poodle extends dog { public $type; public function set_type($height) { if ($heighttype = Toy ; } elseif ($height>15) { $this->type = Standard ; } else { $this->type = Miniature ; } } }
  • Inheritance example The American Kennel Club (AKC) recognizes three sizes of poodle - Standard, Miniature, and Toy class poodle extends dog { public $type; public function set_type($height) { if ($heighttype = Toy ; } elseif ($height>15) { $this->type = Standard ; } else { $this->type = Miniature ; } } } class poodle extends dog { Note the use of the extends keyword to indicate that the poodle class is a child of the dog class
  • Inheritance example $puppy = new poodle( Oscar ); $puppy->set_type(12); // 12 inches high! echo Poodle is called {$puppy->name} , ; echo of type {$puppy->type} , saying ; echo $puppy->bark();
  • a poodle will always Yip!
    • It is possible to over-ride a parent method with a new method if it is given the same name in the child class..
    • class poodle extends dog {
    • public function bark() {
    • echo Yip!;
    • }
    • }
  • Child Constructors?
    • If the child class possesses a constructor function, it is executed and any parent constructor is ignored .
    • If the child class does not have a constructor, the parents constructor is executed.
    • If the child and parent does not have a constructor, the grandparent constructor is attempted
    • etc.
  • Deleting objects
    • So far our objects have not been destroyed till the end of our scripts..
    • Like variables, it is possible to explicitly destroy an object using the unset () function.
  • There is a lot more
    • We have really only touched the edge of object orientated programming
    • But I dont want to confuse you too much!
  • PHP4 vs. PHP5
    • OOP purists will tell you that the object support in PHP4 is sketchy. They are right, in that a lot of features are missing.
    • PHP5 OOP system has had a big redesign and is much better.
    • but it is worth it to produce OOP
    • code in either PHP4 or PHP5
  • Thank you