PHP Functions Essential Reference

srand

void srand(int seed) 

Seeds the random number generator with the given argument.

Returns:

Nothing

Description:

Seeds the random number generator. It’s always a good idea to do this before using the rand() function. Any number can be used to seed the generator, but as a general rule the more random the number you start with, the more random the number you’ll get. Usually, using something like mktime() yields a suitable number. Another common solution is to combine process IDs, the time, and the client’s IP number to produce a more random seed.

Version:

PHP 3, PHP 4

See also:

getrandmax() 
mt_getrandmax() 
mt_rand() 
mt_srand() 
rand() 

Example:

Seed the random number generator

srand(mktime()); echo "A random number: ", rand();