Vague Error

<?php
// In the code below, we have a simple array of contact names. 
// We want to use the $contacts array to fill in the hardcoded list of names an email addresses.
// To hold the email as well as the name for each contact, we need a multidimensional array,
// meaning each person in the contact list will have their own array. The first step is to make each person
// their own single item ASSOCIATIVE array, using 'name' as the key for these internal arrays.

//edit this array
//$contacts = array('Alena Holligan', 'Dave McFarland', 'Treasure Porth', 'Andrew Chalkley');

$contacts[] = [
  'name' => 'Alena Holligan'
];

$contacts[] = [
  'name' => 'Dave McFarland'
];

$contacts[] = [
  'name' => 'Treasure Porth'
];

$contacts[] = [
  'name' => 'Andrew Chalkey'
];

echo "<ul>\n";
//$contacts[0] will return 'Alena Holligan' in our simple array of names.
echo "<li>Alena Holligan : alena.holligan@teamtreehouse.com</li>\n";
echo "<li>Dave McFarland : dave.mcfarland@teamtreehouse.com</li>\n";
echo "<li>Treasure Porth : treasure.porth@teamtreehouse.com</li>\n";
echo "<li>Andrew Chalkley : andrew.chalkley@teamtreehouse.com</li>\n";
echo "</ul>\n";