Hashmap vs arrays

PHP
1

what are the performance issues related to hashmap vs arrays.

also is this true:
hash(“duck”) = 1
hash(“pond”) = 5

if the hash function maps “duck” to 1 and “pond” to 5, will the array in memory look like this:

[0] => “”
[1] => “duck”
[2] => “”
[3] => “”
[4] => “”
[5] => “pond”

so therefore hashmaps create unused space… ?

2

a friend of mine used Hash method to combine data… confused the hell out of me… i’m still new to it.

3

I think the OP meant hash functions not hash lists. Hash functions process input using string / math manipulations. So in fact, there is no “unused space” as it is calculated when called, maybe some overused CPU cycles

4

Do you mean if you create an array like this:


array(
  1 => "duck",
  5 => "pond"
)

Then maybe but in PHP there is no distinction between hashes and arrays, they are both one in the same in PHP.
See: http://us.php.net/manual/en/language.types.array.php