Calculates the difference between two strings.
Usage:
<?php
include 'vendor/autoload.php';
$diff = str_diff(
'I am inevitable !',
'I am Iron Man !'
);
echo $diff['common_start']; // "I am"
echo $diff['common_end']; // " !"
echo $diff['left']; // "inevitable"
echo $diff['right']; // "Iron Man"