## Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

### Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

# Can anyone tell me why the below code outputs the array in reverse?

Quiz Question 1 of 8 What does the following code display?

```\$numbers = array(1,2,3,4);
\$total = count(\$numbers);
\$sum = 0;
\$output = "";
\$loop = 0;

foreach(\$numbers as \$number) {
\$loop = \$loop + 1;
if (\$loop < \$total) {
\$output = \$number . \$output;
}
}

echo \$output;

?>
```

Thanks all

STAFF

Hi there, Matt Nickolls! I took the liberty of adding some markdown to your question so that it is a bit easier to read. Sure, I can guide you through why this is the case.

The first thing to keep in mind is that `\$output` is an empty string and we're going to be concatenating it onto the end of another string each iteration.

Here's the loop part:

```foreach(\$numbers as \$number) {
\$loop = \$loop + 1;
if (\$loop < \$total) {
\$output = \$number . \$output;
}
}
```

At the first iteration, `\$number` will be equal to 1. `\$loop` will also be set to 1. The `\$total` variable holds the number of numbers in that array. So it is 4 and will not change. Is 1 less than 4? Yes, it is. So take the empty string and set it to the `\$number` concatenated with the empty string and overwrite `\$output`. So now `\$output` is the result of "1" concatenated with `""`, which gives `\$output` the value of `"1"`.

Now onto the second iteration. The `\$number` is now 2 and `\$loop` is now 2. Is 2 less than 4? Yes, it is. So take `\$output` which is now the string `"1"` and set it equal to the number (which is 2) concatenated with \$output ("1") on the end. Now `\$output` is equal to `"21"`. Because we're taking the number and concatenating the previous version of `\$output` on the end.

Third iteration. `\$number` is now 3. `\$loop` is 3. Is 3 less than 4? Yup. \$output is "21". So we take the number (which is 3) and concatenate `"21"` onto the end of 3 and overwrite `\$output`. The `\$output` variable now has a value of "321".

Final iteration. `\$number` is now 4. `\$loop` is 4. Is 4 less than 4? Nope. Loop ends here.

So then we echo out the value of `\$output` which is `"321"`.

Hope this helps!

It's the order of the concatenation that's important here. If this line:

```\$output = \$number . \$output;
```

```\$output = \$output . \$number;