I don't know what I am doing wrong (task 2 of 7)

Matthew's answer is correct, but also as a side note your code was not far off from being correct using PHP5 shorthand array.

This would of also been valid:

<?php

$movie = [];
$movie['title'] = 'The Empire Strikes Back';

?>

This is the PHP 5 shorthand for declaring an empty array (which you got correct):

<?php

$movie = [];

?>

and this is the PHP5 shorthand for array push (which adds the value to the end of the array):

<?php

$movie[] = value;  /* Without Associative Key */
$movie[key] = value;  /* With Associative Key */

?>

This is the more modern way to declare an array, I find it a lot cleaner and easier to read than the old way. But it is not valid if your server's PHP version is less than 5.4 (Which is unlikely nowadays, especially with the recent release of PHP7).

You'd want to do either of these 2 statements:

<?php
$movie = array(
"title" => "The Empire Strikes Back"
);
?>

---or---

<?php
$movie = array();
$movie["title"] = "The Empire Strikes Back";

Thank you Matthew!