In PHP, an abstract class is a class that cannot be instantiated, meaning you cannot create an object from it. It is a class that is only meant to be extended by other classes. Abstract classes are declared using the abstract keyword, and they may contain abstract and non-abstract methods.
Abstract methods are declared using the abstract keyword, and they do not contain any implementation code. Instead, they just declare the method signature, including the method name, input parameters, and return type. The implementation of these methods is left to the classes that extend the abstract class.
Here is an example of an abstract class in PHP:
abstract class Shape {
protected $color;
public function __construct($color) {
$this->color = $color;
}
public function getColor() {
return $this->color;
}
abstract public function getArea();
}
In this example, Shape is an abstract class that has a constructor and a non-abstract method getColor(). It also has an abstract method getArea(), which does not have an implementation.
Classes that extend the Shape class will need to implement the getArea() method, which will provide an implementation for calculating the area of the shape.
To implement the abstract class concept in PHP, the following basic rules must be followed:
- The abstract keyword must be used before the class name to define an abstract class.
- Abstract classes can have abstract methods, non-abstract methods, and class properties.
- Abstract methods are declared using the abstract keyword and do not have a body. They must be implemented by the child class.
- Non-abstract methods in the abstract class can have a body and can be directly used by the child class.
- The child class must implement all the abstract methods of the parent abstract class.
- Abstract classes cannot be instantiated directly. They must be inherited by the child class, and the child class must be instantiated to use the methods and properties of the abstract class.
