Description:
------------
---
From manual page: http://www.php.net/function.hash-hmac
---

This is a mix of a doc problem and a feature request.

Simply said the doc says, that one should refer to the hash_algos funtion to see what can be used for HMACs but that's not entirely true, as it contains algorithms that cant be used for HMAC.

while I know that it's totally stupid to use things like CRC32 or Adler32 for HMACs, but this doesnt change that there isnt a proper list fuunction for HMACs.



Test script:
---------------
<?php
$garray=[];
$barray=[];

foreach (hash_algos() as $hashx) {
  $h=hash_hmac($hashx,"hello","hello");
  if($h) {$garray[$hashx]=$h;} else {$barray[$hashx]=$h;}
}
var_dump($garray,$barray);
if(count($barray)>0) {
  echo "hashes that dont work for HMAC are: ".implode(", ",array_keys($barray));
}
else {
  echo "all hashes are compatible with HMAC"
}
?>

Expected result:
----------------
a list of algos and their HMACs, an empty array for the hashes that dont work as well as the output "all hashes are compatible with HMAC"

Actual result:
--------------
2 Lists of algos one which has working hmacs and another which has false as the value, as well as the output:

"hashes that dont work for HMAC are: adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat"