Object-Oriented Programming with PHP (part 1)
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This document provides an introduction to object-oriented programming concepts in PHP, including: - Classes define types of entities and objects are individual instances of a class. For example, Dog is a class and Lassie is a Dog object. - Classes contain methods and properties to define their behavior and attributes. - The $this variable refers to the current object instance and is used to access methods and properties. - Constructors and destructors are special methods that are called when an object is created or destroyed. - Methods and properties can be public, private, or protected to control accessibility.
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Object-Oriented Programming with PHP (part 1)
- 1. Object-Oriented Programming with PHP Part 1 by Bozhidar Boshnakov
- 2. Recap • We talked about – Loops – Conditional statements – Functions and return values – Include and require – Variables scope
- 3. Table of contents • Classes and objects • Methods and properties • Scope
- 4. • The idea of Object Oriented Programming is to move the architecture of an application closer to real world – Classes are types of entities – Objects are single units of a given class – Example – Dog is a class, your dog Lassie is an object of class Dog – Classes have methods and properties – Classes and objects help to create well- structured application
- 5. • Declaring of a class in PHP can be done anywhere in the code – Two special methods: constructor and destructor • Executed when creating or destroying new object of this class • Used to initialize or cleanup properties and etc. class Dog { … // declare methods and properties }
- 6. • Class definition begins with the class keyword, followed by its name and methods and properties list – Objects of class (instances) are created with the keyword new class A { function foo () { echo "foo here!"; } } $myFirstObject = new A(); $myFirstObject->foo(); // prints out "foo here!";
- 7. • Each class can have only one constructor – All parameters of the creating of the object are passed to the constructor class A { function __construct ($bar) { echo $bar; } function foo () { echo "foo here!"; } } $myFirstObject = new A('test'); // print 'test'
- 8. • Class can have unlimited number of properties • The $this variable points to the current object – called execution context class A { var $bar; function __construct ($bar) { $this->bar = $bar; } function myPrint () { echo $this->bar; } } $myFirstObject = new A('test'); $myFirstObject->myPrint();
- 9. • Class can specify default value for a property • Properties can be accessed from the outside world class A { var $bar = 'default value'; … class A { var $bar = 'default value'; … } $obj = new A; echo $obj->bar;
- 10. • Example of what $this is • Can be used to access methods too class A { var $bar; function __construct ($bar) { $this->bar = $bar; } function myPrint () { echo $this->bar; } } $myFirstObject = new A('test'); $myFirstObject->myPrint(); // prints 'test' $anotherObject = new A('foo'); $anotherObject ->myPrint(); // prints 'foo';
- 11. • Each class can have only one destructor – Must be public – Destructors are automatically called when script is shutting down class A { function __construct ($name) { $this->fp = fopen ($name, 'r'); } function __destruct () { fclose($this->fp); } } $myFirstObject = new A('test');
- 12. • Each method and property has a scope – It defines who can access it – Three levels – public, protected, private • Private can be access only by the object itself • Protected can be accessed by descendant classes (see inheritance) • Public can be accessed from the outside world – Level is added before function keyword or instead of var • var is old style (PHP 4) equivalent to public – Constructors always need to be public
- 13. class A { private $bar; public function __construct ($bar) { $this->bar = $bar; } public function myPrint () { echo $this->bar; } } $myFirstObject = new A('test'); $myFirstObject->myPrint(); // prints 'test' // this will not work: echo $myFirstObject->bar;
- 14. • Resources – http://php-uroci.devbg.org/ – http://academy.telerik.com/ – http://www.codecademy.com/