php question, best way for random numbers?

[fris]

Whats the best way for random number generation?

this is what im using now

<?
mt_srand ((double) microtime() * 1000000);
$random = mt_rand(1,100);
echo $random;
?>

[HorseShit]

not sure but im sure our channel coders will know

[grumpy]

you dont need the mt_srand ((double) microtime() * 1000000);
Its build in in the mt_rand

[Libertine]

Originally Posted by grumpy

you dont need the mt_srand ((double) microtime() * 1000000);
Its build in in the mt_rand

Yep. As of 4.2, seeding is no longer needed, if I recall correctly.

mt_rand() will do for most purposes, but if you need pseudo-random data for purposes related to cryptography, keep in mind that mt_rand uses a mersenne twister, which is rather weak. So, in those cases, getting your pseudo-random data from /dev/urandom is a better option.

[leek]

Note: As of PHP 4.2.0, there is no need to seed the random number generator with srand() or mt_srand() as this is now done automatically.

RTFM

[Brujah]

I believe that you don't really need to use mt_srand with php 5.2.1+
You could use uniqid as a seed, or data from /dev/random

[Brujah]

Originally Posted by grumpy

you dont need the mt_srand ((double) microtime() * 1000000);
Its build in in the mt_rand

True, but there was a fuss about it being insecure until 5.2.1+ I think

[fris]

im just getting a random number for random image headers, have 10 headers, want to rotate through them

[Libertine]

Originally Posted by fris

im just getting a random number for random image headers, have 10 headers, want to rotate through them

mt_rand will do fine, then.

The other stuff only comes into play when dealing with things where security is an issue, like when a forgotten admin password of a site gets reset on request (which actually was a security hole in Joomla and WP).

[yuu.design]

Originally Posted by fris

im just getting a random number for random image headers, have 10 headers, want to rotate through them

<?php
$image = rand(1,10);

echo "<img src=\"$image.jpg\" width=\"\" height=\"\" alt=\"\" />";

?>

Like above, rand() will work fine for what you need.