PHP中是否保证关联数组的顺序？

当我在PHP中的associatve数组上执行foreach循环时,执行它的顺序是它的定义顺序.

例如：

$arr = array("z" => "z", "a" => "a", "b" => "b");

foreach($arr as $key => val)
  print("$key: $val\n");

输出：

z: z
a: a
b: b

而

$arr = array("a" => "a", "b" => "b", "z" => "z");

输出：

a: a
b: b
z: z

那么我的问题是：这种行为是在规范级别定义的吗？我可以合理地确定在将来的PHP版本中不会更改此行为吗？

解决方法:

从PHP Manual

An array in PHP is actually an ordered
map. A map is a type that associates
values to keys. This type is optimized
for several different uses; it can be
treated as an array, list (vector),
hash table (an implementation of a
map), dictionary, collection, stack,
queue, and probably more.

和

Arrays are ordered. The order can be
changed using varIoUs sorting
functions.

因此,您可以确定(至少目前)订单将得到维护.如果这种行为发生变化,我会非常惊讶,因为它是明确说明的,因此会有大量依赖它的代码.