The upper-bound of this value is platform-independent. PHP implements the 32-bit version of the Mersenne Twister ("mt"), so the maximum possible value is 2**31 - 1 (2147483647).
(PHP 4, PHP 5, PHP 7)
mt_getrandmax — Show largest possible random value
Returns the maximum value that can be returned by a call to mt_rand().
Returns the maximum random value returned by a call to
mt_rand() without arguments, which is the maximum value
that can be used for its max parameter without the
result being scaled up (and therefore less random).
Example #1 Calculate a random floating-point number
<?php
function randomFloat($min = 0, $max = 1) {
return $min + mt_rand() / mt_getrandmax() * ($max - $min);
}
var_dump(randomFloat());
var_dump(randomFloat(2, 20));
?>
The above example will output something similar to:
float(0.91601131712832) float(16.511210331931)
The upper-bound of this value is platform-independent. PHP implements the 32-bit version of the Mersenne Twister ("mt"), so the maximum possible value is 2**31 - 1 (2147483647).
On both 32 and 64-bit systems (OS X and Linux), mt_getrandmax() returns 2147483647 for me, i.e. ~2^31.