Description:
------------
From the docs for rand: "In older versions of PHP, you 
had to seed the random number generator before use with 
srand(). Since 4.2.0 this is no longer necessary."

The implication is that rand seeds the RNG the first 
time it is called, unless srand has been previously 
called; however, rand seeds the RNG every time (or 
until srand is explicitly called). This results in a 
significant increase in running time (about an order of 
magnitude).

The above also applies to mt_rand, except that the 
performance penalty is greater (apparently because its 
seed-generation algorithm is more expensive).

(the patch to ext/standard/rand.c to correct the 
problem is trivial)

Reproduce code:
---------------
// t1.php
<?
for ($i=0; $i<100000; $i++) rand(0,10);
?>

// t2.php
<?
srand();
for ($i=0; $i<100000; $i++) rand(0,10);
?>

Actual result:
--------------
$ time php t1.php

real    0m0.729s
user    0m0.650s
sys     0m0.080s

$ time php t2.php

real    0m0.101s
user    0m0.100s
sys     0m0.000s