<?php

abstract class Person {

  abstract public function getName();

  public function getIntroduction() {
    return sprintf(
      'My name is %s',
      $this->getName()
    );
  }
}

class Joaquin extends Person {

  public function getName() {
    return 'Joaquin';
  }
}

$joaquin = new Joaquin();
print $joaquin->getIntroduction();
// This prints "My name is Joaquin"