PHP: rfc:use-php_mt_rand

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====== PHP RFC: Use php_mt_rand() instead of php_rand() ======
  * Version: 0.9
  * Date Created: 2014-07-17
  * Author: Yasuo Ohgaki, yohgaki@php.net
  * Status: Withdrawn
  * First Published at: http://wiki.php.net/rfc/use-php_mt_rand

https://wiki.php.net/rfc/rng_fixes tooke care of this RFC. Withdrawn.

===== Introduction =====
Both php_rand() and php_mt_rand() internal function provides pseudo random numbers. php_rand() uses system random function which has less randomness compare to MT rand. There are few places that use php_rand() currently.

  * http://lxr.php.net/search?q=php_rand&defs=&refs=&path=&hist=&project=PHP_5_5

These functions could use php_mt_rand() instead of php_rand() to improve randomness.

  * Most system uses random() function that has cycle of 16 * ((2^31) - 1)
  * MT rand has cycle of 2^19937-1 which is much larger than random().


===== Proposal =====

  - Add automatic seeding to php_mt_rand() like php_rand() currently is.
  - Use php_mt_rand() where php_rand() is used.
  - Add 64 bit MT rand for 64 bit platforms. http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt64.html
  - Use php_mt_rand()/php_mt_srand() for rand()/srand() PHP function.
  - Rename rand()/srand() to rand_XXX()/srand_XXX() - name is TBD.

Note: rand() (or rand_XXX) uses php_rand(), NOT php_mt_rand().

===== Backward Incompatible Changes =====

Game that expects the same pseudo random sequences. These apps may use mt_srand() to get fixed random 
sequences and adjust their apps if it is needed.

64 bit platforms get different pseudo random sequences. 

===== Proposed PHP Version(s) =====

  * PHP 5.x+

===== RFC Impact =====
==== To SAPIs ====
None

==== To Existing Extensions ====

Standard module
  * shuffle http://jp1.php.net/manual/en/function.shuffle.php
  * array_rand http://jp1.php.net/manual/en/function.array-rand.php
  * str_shuffle http://jp1.php.net/manual/en/function.str-shuffle.php
  * password_hash http://jp1.php.net/manual/en/function.password-hash.php (Used to generate salt)
  * rand http://jp1.php.net/manual/en/function.rand.php

Mcrypt
  * mcrypt_create_iv() http://jp1.php.net/manual/en/function.mcrypt-create-iv.php (When true RNG is not used)

==== To Opcache ====
None

==== New Constants ====
None

==== php.ini Defaults ====
If there are any php.ini settings then list:
  * hardcoded default values
  * php.ini-development values
  * php.ini-production values

None.

===== Open Issues =====
Determine rand() rename candidate.

===== Unaffected PHP Functionality =====
php_rand()/php_srand() remains. Therefore, modules that are using them are not affected.

===== Future Scope =====
None.

===== Proposed Voting Choices =====

VOTE: 2014/XX/XX - 2014/XX/XX
 
If you agree to apply stronger pseudo random number, please vote 'yes'.
<doodle title="Use php_mt_rand(): Proposal 1 to 3" auth="yohgaki" voteType="single" closed="true">
   * Yes
   * No
</doodle>

 \\ If you would like to have MT rand for rand() function, please vote 'yes'.
<doodle title="Use php_mt_rand() for rand() function: Proposal 4" auth="yohgaki" voteType="single" closed="true">
   * Yes
   * No
</doodle>

 \\ Please choose 'yes' or 'no' even if you vote 'no' for previous.
<doodle title="Rename rand(): Proposal 5" auth="yohgaki" voteType="single" closed="true">
   * Yes
   * No
</doodle>

Thank you for voting!

State whether this project requires a 2/3 or 50%+1 majority (see [[voting]])

===== Patches and Tests =====

TBD

===== Implementation =====
After the project is implemented, this section should contain 
  - the version(s) it was merged to
  - a link to the git commit(s)
  - a link to the PHP manual entry for the feature

===== References =====
Links to external references, discussions or RFCs

  * https://bugs.php.net/bug.php?id=66718
  * http://lxr.php.net/search?q=php_rand&defs=&refs=&path=&hist=&project=PHP_5_5


===== Rejected Features =====
Keep this updated with features that were discussed on the mail lists.
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