# Flatten Array

Take a nested list and return a single flattened list with all values except nil/null.

The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.

For Example

input: [1,[2,3,null,4],[null],5]

output: [1,2,3,4,5]

## Making the Test Suite Pass

1. Get [PHPUnit].

        % wget --no-check-certificate https://phar.phpunit.de/phpunit.phar
        % chmod +x phpunit.phar

2. Execute the tests for an assignment.

        % phpunit.phar wordy/wordy_test.php

[PHPUnit]: http://phpunit.de


## Source

Interview Question [https://reference.wolfram.com/language/ref/Flatten.html](https://reference.wolfram.com/language/ref/Flatten.html)

## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.