2 `Map` is an ordered dictionary
-style collection. HHVM provides a native
3 implementation
for this class. The PHP class definition below is not
4 actually used at run time
; it is simply provided
for the typechecker and
for
7 Like all objects in PHP
, `Map`s have reference
-like semantics. When a caller
8 passes a `Map` to a callee
, the callee can modify the `Map` and the caller
9 will see the changes. `Map`s
do not have
"copy-on-write" semantics.
11 `Map`s preserve insertion order of
key/value pairs. When iterating over a
12 `Map`
, the
key/value pairs appear in the order they were inserted. Also
,
13 `Map`s
do not automagically
convert integer-like `string` keys
(ex. `
"123"`)
16 `Map`s only support `
int` keys and `string` keys.
If a
key of a different
17 type is used
, an exception will be thrown.
19 `Map`s support `$m
[$k
]` style syntax
for getting and setting
values by
key.
20 `Map`s also support `isset
($m
[$k
])` and `empty
($m
[$k
])` syntax
, and they
21 provide similar semantics as arrays. Adding an element with square bracket
22 syntax `
[]` is supported either by providing a
key between the brackets or
23 a `Pair`
on the right
-hand side. e.g.
,
24 `$m
[$k
] = $v` is supported
25 `$m
[] = Pair
{$k
, $v
}` is supported
26 `$m
[] = $v` is not supported.
28 `Map`s
do not support iterating
while new keys are being added or elements
29 are being removed. When a new
key is added or an element is removed
, all
30 iterators that point to the `Map` shall be considered invalid.
32 @guide
/hack
/collections
/introduction
33 @guide
/hack
/collections
/classes
