Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

PHP PHP Arrays and Control Structures PHP Loops For Looping

question about the use of isset() in the challange

So i figure out the challange but im not 100% sure what's going on:

for ( $i = 1; $i <= 100; $i++ ) {
    echo $i . "\n";
    //if the key exists in the array
    if(isset($facts[$i])) {
        //we show the value of this key
      echo $facts[$i] . "\n";


in the if statment isset is checking if there is an element in the current position of the $i , the $i is lets say in the 57 iteration so

$facts[$i] === $facts["57"]

if there is an element that exists in the current iteration the evulation of the if statement return TRUE if not it return NULL. so in the above example $facts["57"] return true because $i has the same value as one of the existing keys of the $facts array

am i right on how the use of isset() function works here, that's what is happening under the hood?

1 Answer

According to the PHP docs isset returns TRUE if var exists and has any value other than NULL. FALSE otherwise.