basic classes.php

<?php

class Foo {

    public function __construct($name) {

        $this->name = $name;

    }

    public function getName() {
        return $this->name;
    }

}

class Bar extends Foo {

    public function __construct($name, $job) {

        parent::__construct($name);
        $this->job = $job;

    }

    public function getUpperName() {
        return strtoupper($this->name);
    }

}



$foo = new Foo('JLo');
$foo->name; // "JLo"
$foo->job; // null
$foo->getUpperName(); // Exception

$bar = new Bar('JLo', 'WebDev');
$bar->name; // "JLo"
$bar->job; // "WebDev"
$bar->getUpperName(); // "JLO"