why doesn't this work for the answer?

<?php
//edit this array
//$contacts = array('Alena Holligan', 'Dave McFarland', 'Treasure Porth', 'Andrew Chalkley');
$contacts['Alena Holligan'] = 'alena.holligan@teamtreehouse.com';
$contacts['Dave McFarland'] = 'dave.mcfarland@teamtreehouse.com';
$contacts['Treasure Porth'] = 'treasure.porth@teamtreehouse.com';
$contacts['Andrew Chalkley'] = 'andrew.chalkley@teamtreehouse.com';
//var_dump($contacts);

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";