TMap implements a collection that takes key-value pairs.
You can access, add or remove an item with a key by using
{@link itemAt}, {@link add}, and {@link remove}.
To get the number of the items in the map, use {@link getCount}.
TMap can also be used like a regular array as follows,
$map[$key]=$value; // add a key-value pair
unset($map[$key]); // remove the value with the specified key
if(isset($map[$key])) // if the map contains the key
foreach($map as $key=>$value) // traverse the items in the map
$n=count($map); // returns the number of items in the map