The magic function is rand() which returns a random integer. There are two uses

int rand  (void)
int rand (int $min , int $max)

If you don’t supply any variables, rand() returns a random integer between 0 and RAND_MAX. RAND_MAX is usually 32768 on Windows systems, if you need a higher value, then you need to specify a $min and $max variable to generate a larger range.

If you supply a range of integers to rand(), then the range of possible values between $min and $max inclusive.

Examples

<?php echo rand(); ?>

Could return integers such as 7734, 1981, 2, 0, 30929 etc.

<?php echo rand(1,5) ?>

Will return one of the following: 1,2,3,4,5.

<?php echo rand(15000,50000) ?>

Will return any integer between (and including) 15000 and 50000.