Skip to main content

reproducible random number series


How can i get a series of reproducible pseudorandom numbers in PHP?



In older versions of PHP i could do that just by using the same seed in the RNG , but it does not work anymore since PHP has changed the way rand and mt_rand works.



Please also see this comment in PHP.net page:




Keep in mind that the Suhosin patch which is installed by default on many PHP-installs such as Debian and DirectAdmin completely disables the srand and mt_srand functions for encryption security reasons. To generate reproducible random numbers from a fixed seed on a Suhosin-hardened server you will need to include your own pseudorandom generator code.




link of that comment: http://www.php.net/manual/en/function.srand.php#102636



Is there any solution ready? I do not have the time nor the experience to create my own pseudo-random generator code.



My goal is to have a code




<?php
//( pseudo random code here...)
$the_seed = 123; // 123 is just a number for demo purposes, NOT a static number
//...i hope you get the idea. It's just a hardcoded seed,
// it could be a seed based on a user-id, a date etc...
// we need the same output for a given seed.
//( pseudo random code here...)

// ...and finally
echo $the_random_number;
?>



so everytime i visit this page i should get the same number.


Source: Tips4allCCNA FINAL EXAM

Comments

  1. One of the best random number algorithms by some metrics is Mersenne Twister.
    You can find a pure PHP version here (there are others).

    You can then call:

    init_with_integer($integer_seed)


    and get the same output (for a given seed) every time.

    ReplyDelete

Post a Comment

Popular posts from this blog

Why is this Javascript much *slower* than its jQuery equivalent?

I have a HTML list of about 500 items and a "filter" box above it. I started by using jQuery to filter the list when I typed a letter (timing code added later): $('#filter').keyup( function() { var jqStart = (new Date).getTime(); var search = $(this).val().toLowerCase(); var $list = $('ul.ablist > li'); $list.each( function() { if ( $(this).text().toLowerCase().indexOf(search) === -1 ) $(this).hide(); else $(this).show(); } ); console.log('Time: ' + ((new Date).getTime() - jqStart)); } ); However, there was a couple of seconds delay after typing each letter (particularly the first letter). So I thought it may be slightly quicker if I used plain Javascript (I read recently that jQuery's each function is particularly slow). Here's my JS equivalent: document.getElementById('filter').addEventListener( 'keyup', function () { var jsStart = (new Date).getTime()...

Is it possible to have IF statement in an Echo statement in PHP

Thanks in advance. I did look at the other questions/answers that were similar and didn't find exactly what I was looking for. I'm trying to do this, am I on the right path? echo " <div id='tabs-".$match."'> <textarea id='".$match."' name='".$match."'>". if ($COLUMN_NAME === $match) { echo $FIELD_WITH_COLUMN_NAME; } else { } ."</textarea> <script type='text/javascript'> CKEDITOR.replace( '".$match."' ); </script> </div>"; I am getting the following error message in the browser: Parse error: syntax error, unexpected T_IF Please let me know if this is the right way to go about nesting an IF statement inside an echo. Thank you.