Abstract Class in php

➔ PHP 5 incorporates the concept of abstract classes and abstract methods.

➔ The abstract class defined is not intended to be used to create an object from it; the abstract class has at least one abstract method that must be initialized to mean an abstract class.

➔ Abstract methods only declare the method name and parameter list (method signature), but do not define the inner executable (nobody like interface methods).

Inherit the abstract class

➔ When a class inherits an abstract class, it must define (implement) all abstract methods in the abstract class that it inherits.

➔ In addition, methods must have the same visibility level defined or higher than the specified visibility in the parent class (public, private, protected)

Example

➔ AbstractClass abstract class definition

<?php

abstract class AbstractClass
{
    // Force Extending class to define this method
    abstract protected function getValue();
    abstract protected function prefixValue($prefix);

    // Common method
    public function printOut()
    {
        print $this->getValue() . "\n";
    }
}

?>

➔ Creates a ConcreteClass1 child class inheriting AbstractClass

<?php
class ConcreteClass1 extends AbstractClass
{
    protected function getValue()
    {
        return "ConcreteClass1";
    }

    public function prefixValue($prefix)
    {
        return "{$prefix}ConcreteClass1";
    }
}
?>

➔ Creates a ConcreteClass2 child class inheriting AbstractClass

<?php
class ConcreteClass2 extends AbstractClass
{
    protected function getValue()
    {
        return "ConcreteClass2";
    }

    public function prefixValue($prefix)
    {
        return "{$prefix}ConcreteClass2";
    }
}
?>

➔ Creates $class1 $class2 object

<?php
$class1 = new ConcreteClass1;
$class1->printOut();
echo $class1->prefixValue("Foo_") . "\n";

$class2 = new ConcreteClass2;
$class2->printOut();
echo $class2->prefixValue("Foo_") . "\n";
?>

➔ Show result

ConcreteClass1
Foo_ConcreteClass1
ConcreteClass2
Foo_ConcreteClass2