PHP Abstract Class

Question

PHP Abstract Classes
What is the output of the following code?
abstract class Calc {
abstract public function calculate($param);
protected function getConst() { return 4; }
}
class FixedCalc extends Calc {
public function calculate($param) {
return $this->getConst() + $param;
}
}
$obj = new FixedCalc();
echo $obj->calculate(38);

Answer 1

Abstract classes are not instantiable, they were meant to be extended by other classes which were supposed to provide the implementation of the abstract class' functions.

So here, `FixedCalc` extends abstract class `Calc`, and provides an implementation of the `calculate()` function. The implementation of `calculate()` function inside `FixedCalc` class defines that the function returns whatever value returned by the protected method `getConst()` plus the value of argument <$param>.

Basically, the implementation of `calculate()` function returns the value returned by `getConst()` (value 4) plus the value of argument <$param> (value 38).

And in the end of the snippet, you output that value into the document's body.

Hth, cmiiw