Difference Of Squares in PHP
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
1  exercism fetch php differenceofsquares

Difference Of Squares
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
The square of the sum of the first ten natural numbers is (1 + 2 + ... + 10)² = 55² = 3025.
The sum of the squares of the first ten natural numbers is 1² + 2² + ... + 10² = 385.
Hence the difference between the square of the sum of the first ten natural numbers and the sum of the squares of the first ten natural numbers is 3025  385 = 2640.
Running the tests

Go to the root of your PHP exercise directory, which is
<EXERCISM_WORKSPACE>/php
. To find the Exercism workspace run1
% exercism debug  grep Workspace

Get PHPUnit if you don't have it already.

Execute the tests:
1
% ./phpunit.phar differenceofsquares/differenceofsquares_test.php
Source
Problem 6 at Project Euler http://projecteuler.net/problem=6
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.