//If the search_element is included, then only the keys matching that particular element are returned; otherwise, all keys constituting the array are returned.
//Its syntax is: array array_keys (array array, mixed [search_element])
//use array_keys() to return the key of a given element:
$wines = array ("A" => "a","Q" => "q","E" => "e");
$labels = array_keys($wines);
print $labels;
print '
';
$labels = array_keys($wines, "a");
print_r $labels;
?>