<?php
$array = array(11 => 14,
10 => 9,
12 => 7,
13 => 7,
14 => 4,
15 => 6);
echo array_search(max($array), $array);
?>
array_search() return values:
Returns the key for needle if it is found in the array, FALSE otherwise.
If needle is found in haystack more than once, the first matching key is returned. To return the keys for all matching values, use array_keys() with the optional search_value parameter instead.