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Questions and Answers
In PHP, a class is an instance of an object.
False
The public access modifier is used to declare private properties in a class.
False
A constructor is a method that is called when an object is deleted.
False
Method overriding is a concept of polymorphism where a parent class provides a different implementation of a method already defined in its child class.
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Encapsulation is the concept of showing only essential features to the outside world.
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In PHP, an abstract class can be instantiated.
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A static method can only be accessed by creating an instance of the class.
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Inheritance is a concept where a parent class inherits properties and methods from a child class.
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Study Notes
Object-Oriented Programming in PHP
Classes and Objects
- A class is a blueprint for creating objects.
- An object is an instance of a class.
- Classes define properties (data) and methods (functions).
Class Syntax
-
class ClassName { // properties and methods } -
classkeyword is used to declare a class.
Properties (Data Members)
- Declared inside the class using the
public,private, orprotectedaccess modifiers. - Can be of any data type (string, integer, array, etc.).
- Examples:
public $name;,private $age;
Methods (Functions)
- Declared inside the class using the
functionkeyword. - Can take arguments and return values.
- Examples:
public function greet() { echo "Hello!"; }
Constructors
- Special method called when an object is created.
- Used to initialize objects with default values.
- Syntax:
__construct()
Inheritance
- A child class can inherit properties and methods from a parent class.
-
extendskeyword is used to inherit from a parent class. - Example:
class Child extends Parent { // properties and methods }
Polymorphism
- Method overriding: a child class provides a different implementation of a method already defined in its parent class.
- Method overloading: multiple methods with the same name but different parameters.
Encapsulation
- Hiding internal implementation details from the outside world.
- Access modifiers (public, private, protected) control access to properties and methods.
Abstraction
- Showing only essential features to the outside world.
- Abstract classes and interfaces define a blueprint for other classes to follow.
Static Keywords
-
staticproperties and methods belong to the class, not instances. - Can be accessed without creating an object.
- Example:
public static function hello() { echo "Hello!"; }
Classes and Objects
- A class is a blueprint for creating objects, and an object is an instance of a class.
- Classes define properties (data) and methods (functions).
Class Syntax
- A class is declared using the
classkeyword followed by the class name and properties and methods in curly braces.
Properties (Data Members)
- Properties are declared inside the class using the
public,private, orprotectedaccess modifiers. - Properties can be of any data type (string, integer, array, etc.).
- Examples of property declarations:
public $name;,private $age;
Methods (Functions)
- Methods are declared inside the class using the
functionkeyword. - Methods can take arguments and return values.
- Examples of method declarations:
public function greet() { echo "Hello!"; }
Constructors
- A constructor is a special method called when an object is created.
- Constructors are used to initialize objects with default values.
- The syntax for a constructor is
__construct().
Inheritance
- A child class can inherit properties and methods from a parent class using the
extendskeyword. - Example of inheritance:
class Child extends Parent { // properties and methods }
Polymorphism
- Method overriding occurs when a child class provides a different implementation of a method already defined in its parent class.
- Method overloading occurs when multiple methods have the same name but different parameters.
Encapsulation
- Encapsulation is the concept of hiding internal implementation details from the outside world.
- Access modifiers (public, private, protected) control access to properties and methods.
Abstraction
- Abstraction is the concept of showing only essential features to the outside world.
- Abstract classes and interfaces define a blueprint for other classes to follow.
Static Keywords
-
staticproperties and methods belong to the class, not instances. -
staticmembers can be accessed without creating an object. - Example of a static method:
public static function hello() { echo "Hello!"; }
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Description
Understand the basics of object-oriented programming in PHP, including classes, objects, properties, and methods.
