<?php
class foo {
    public function printItem($string) {
        echo 'Foo: ' . $string . PHP_EOL;
    }

    public function printPHP() {
        echo 'PHP is great.' . PHP_EOL;
    }
}

class bar extends foo {
    public function printItem($string) {
        echo 'Bar: ' . $string . PHP_EOL;
    }
}

$foo = new foo();
$bar = new bar();
$foo->printItem('baz'); // Output: 'Foo: baz'
$foo->printPHP();       // Output: 'PHP is great'
$bar->printItem('baz'); // Output: 'Bar: baz'
$bar->printPHP();       // Output: 'PHP is great'