- substr: documentation ( source)
- var_dump: documentation ( source)
- str_replace: documentation ( source)
- strrchr: documentation ( source)
<?php
$likes = 'Apple, Samsung, Microsoft';
$portion = strrchr($likes, ',');
$likes = str_replace($portion, (" and" . substr($portion, 1, -1)), $likes);
var_dump($likes);