Chap4 oop class (php) part 2
- 1. Object Oriented programming Chapter4 1 Monica Deshmane(Haribhai V. Desai College,Pune)
- 2. What we learn? •Serialization • Inheritance • Interfaces • Encapsulation 2 Monica Deshmane(Haribhai V. Desai College,Pune)
- 3. • Serialization Monica Deshmane(HaribhaiV. Desai College,Pune) 3
- 4. • the serialize()function converts a storable representation of a value. • To serialize data means to convert a value to a sequence of bits, so that it can be stored in a file, a memory buffer, or transmitted across a network. • String serialize(value); • Value- Specifies the value to be serialized Monica Deshmane(Haribhai V. Desai College,Pune) 4
- 5. • When serializingobject php calls __sleep() before serialization. • This allows ex. Clean up before serialize. • When unserializing object php calls __wakeup() before unserialization. • This allows to convert string of byte stream which returned as value which can be stored anywhere. Monica Deshmane(Haribhai V. Desai College,Pune) 5
- 6. • <?php // classa.inc: classA { public $one = 1; public function show_one() { echo $this->one; } } // page1.php: include("classa.inc"); Monica Deshmane(Haribhai V. Desai College,Pune) 6
- 7. $a = newA; $s = serialize($a); // store $s somewhere where page2.php can find it. file_put_contents('store', $s); // page2.php: // this is needed for the unserialize to work properly. include("classa.inc"); $s = file_get_contents('store'); $a = unserialize($s); // now use the function show_one() of the $a object. $a->show_one(); ?> Monica Deshmane(Haribhai V. Desai College,Pune) 7
- 8. • Inheritance Monica Deshmane(HaribhaiV. Desai College,Pune) 8
- 9. Monica Deshmane(Haribhai V.Desai College,Pune) 9 • Inheritance in OOP = When a class derives from another class. • The child class will inherit all the public and protected properties and methods from the parent class. • In addition, it can have its own properties and methods. • An inherited class is defined by using the extends keyword.
- 10. Example2- <?php class A { public functionf1($string) { echo ”in f1”.$string; } public function f2() { echo ”in f2”; } } class B extends A { public function f1($string) { echo “in B f1”.$string; } } $a = new A(); $b = new B(); $a->f1(‘hi'); // Output: in f1hi' $b->f1(‘hi'); // Output: in B f1hi' ?> Monica Deshmane(Haribhai V. Desai College,Pune) 10
- 11. Scope resolution(::)operator • TheScope Resolution Operator (also called the double colon)is a token that allows access to static, constant, and overridden properties or methods of a class. • When referencing these items from outside the class definition, use the name of the class. • As of PHP 5.3.0, it's possible to reference the class using a variable. The variable's value can not be a keyword (e.g. self, parent and static). Monica Deshmane(Haribhai V. Desai College,Pune) 11
- 12. example • <?php class MyClass{ const CONST_VALUE = 'A constant value'; } $classname = 'MyClass'; echo $classname::CONST_VALUE; // As of PHP 5.3.0 echo MyClass::CONST_VALUE; ?> Monica Deshmane(Haribhai V. Desai College,Pune) 12
- 13. Parent, self Monica Deshmane(HaribhaiV. Desai College,Pune) 13 Three special keywords self, parent and static are used to access properties or methods from inside the class definition. Example #2 :: from inside the class definition <?php class OtherClass extends MyClass { public static $my_static = 'static var'; public static function doubleColon() { echo parent::CONST_VALUE . "n"; echo self::$my_static . "n"; } } $classname = 'OtherClass'; echo $classname::doubleColon(); // As of PHP 5.3.0 OtherClass::doubleColon(); ?>
- 14. Access specifiers: public •<?php class Fruit { public $name; function set_name($n) { // a public function (default) $this->name = $n; } } $mango = new Fruit(); $mango->set_name('Mango'); Monica Deshmane(Haribhai V. Desai College,Pune) 14
- 15. public • Any onecan access • Through out script accessible • By default public Monica Deshmane(Haribhai V. Desai College,Pune) 15
- 16. Access specifiers: private •<?php class Fruit { public $weight; private function set_weight($n) { // a private function $this->weight = $n; } } $mango = new Fruit(); $mango->set_weight('300'); // ERROR ?> Monica Deshmane(Haribhai V. Desai College,Pune) 16
- 17. Private: • Used forInformation hiding • Accessible within class only • Restrict objects from accessing class members Monica Deshmane(Haribhai V. Desai College,Pune) 17
- 18. Access specifiers: protected •<?php class Fruit { public $color; protected function set_color($n) { // a protected function $this->color = $n; } $mango = new Fruit(); $mango->set_color('Yellow'); // ERROR ?> Monica Deshmane(Haribhai V. Desai College,Pune) 18
- 19. protected • Like private •Accessible within class • And also in derived class Monica Deshmane(Haribhai V. Desai College,Pune) 19
- 20. Final keyword- • Finalmethod- • <?php class parentClass { final private function someMethod() { } } class childClass extends parentClass { private function someMethod() { } } ?> -error "Fatal error Such behaviour looks slight unexpected because in child class we cannot know, which private methods exists in a parent class and vice versa. Monica Deshmane(Haribhai V. Desai College,Pune) 20
- 21. Final class • Finalclass A { } Class B extends class A { } //fatal error: can not inherit class Monica Deshmane(Haribhai V. Desai College,Pune) 21
- 22. • The useof final keyword is just like that occurs in Java • In java final has three uses 1) prevent class Inheritance • 2) prevent method overriding or redifination of method in subclass • 3) and to declare constants But the third point seems to be missing from the PHP Monica Deshmane(Haribhai V. Desai College,Pune) 22
- 23. Abstract class methods •Can not create object An abstract class is a class that contains at least one abstract method. An abstract method is a method that is declared, but not implemented in the code. An abstract class or method is defined with the abstract keyword: • <?php abstract class ParentClass { abstract public function Method1(); abstract public function Method2($name, $color); abstract public function Method3() : string; } ?> Monica Deshmane(Haribhai V. Desai College,Pune) 23
- 24. Static • Static keywordused • Without instanciation we can access properties & members of class. • Static used after visibility or access modefiers declaration. • Ex. Public static $a; Monica Deshmane(Haribhai V. Desai College,Pune) 24
- 25. • 4.6 Interfaces MonicaDeshmane(Haribhai V. Desai College,Pune) 25
- 26. interface shape <?php interface myinterface { publicfunction area(); public function volume(); } class cylinder implements myinterface { var $pi=3.14; var $r=3; var $h=3; Monica Deshmane(Haribhai V. Desai College,Pune) 26
- 27. public function area() { $Area=2*$this->pi*$this->r*$this->h; echo"Areaof cylinder is $Area<br>"; } public function volume() { $volume=$this->pi*$this->r*$this->r*$this->h; echo"volume of cylinder is $volume<br>"; } } $c=new cylinder(); $c->area(); $c->volume(); ?> Monica Deshmane(Haribhai V. Desai College,Pune) 27
- 28. Monica Deshmane(Haribhai V.Desai College,Pune) 28 Abstract class 1Abstract function & other defined extends Not pure Abstract class A { Public $a;// allowed property Abstract function f(); …. } Class B extends A{} Interface All are abstract Implements Pure abstract class Inteface A { //not allowed } Class A implements A
- 29. • 4.7Encapsulation Monica Deshmane(HaribhaiV. Desai College,Pune) 29
- 30. Encapsulation • Encapsulation canbe used if the properties of the object are private and updating them through public methods. • It is binding datamembers with member functions. • Encapsulation in PHP can be achieved using the implementation of access specifiers. • __get() and __set() used Monica Deshmane(Haribhai V. Desai College,Pune) 30