PHP Class Abstraction

An abstract class is a class that contains at least one abstract method, which is a method without any actual code in it, just the name and the parameters, and that has been marked as “abstract”.
The purpose of this is to provide a kind of template to inherit from and to force the inheriting class to implement the abstract methods.

abstract
<?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”;
}
}

class ConcreteClass1 extends AbstractClass
{
protected function getValue() {
return “ConcreteClass1”;
}

public function prefixValue($prefix) {
return “{$prefix}ConcreteClass1”;
}
}

class ConcreteClass2 extends AbstractClass
{
public function getValue() {
return “ConcreteClass2”;
}

public function prefixValue($prefix) {
return “{$prefix}ConcreteClass2″;
}
}

$class1 = new ConcreteClass1;
$class1->printOut();
echo $class1->prefixValue(‘FOO_’) .”\n”;

$class2 = new ConcreteClass2;
$class2->printOut();
echo $class2->prefixValue(‘FOO_’) .”\n”;

?>

OUTPUT :
ConcreteClass1 FOO_ConcreteClass1
ConcreteClass2 FOO_ConcreteClass2