(PECL ds >= 1.0.0)
A Map is a sequential collection of key-value pairs, almost identical to an array used in a similar context. Keys can be any type, but must be unique. Values are replaced if added to the map using the same key.
$capacity
$callback
$map
$key
$default
$value
$comparator
$values
$pairs
$initial
$position
$index
$length
Ds\Map::MIN_CAPACITY