What is the purpose of the PHP script mentioned in the forum thread and how does it display the current day of the week?

The purpose of the PHP script mentioned in the forum thread is to display the current day of the week. This is achieved by using the `date()` function in PHP with the 'l' format specifier, which returns the full name of the day of the week.

<?php
$currentDay = date('l');
echo "Today is: " . $currentDay;
?>