An elegant way to return random float between two numbers:
<?php
function random_float ($min,$max) {
return ($min+lcg_value()*(abs($max-$min)));
}
?>
lcg_value
(PHP 4, PHP 5, PHP 7, PHP 8)
lcg_value — Combined linear congruential generator
Description
lcg_value(): float
lcg_value() returns a pseudo random number in the range of (0, 1). The function combines two CGs with periods of 2^31 - 85 and 2^31 - 249. The period of this function is equal to the product of both primes.
Caution
This function does not generate cryptographically secure values, and must not be used for cryptographic purposes, or purposes that require returned values to be unguessable.
If cryptographically secure randomness is required, the Random\Randomizer may be used with the Random\Engine\Secure engine. For simple use cases, the random_int() and random_bytes() functions provide a convenient and secure API that is backed by the operating system’s CSPRNG.
Caution
Scaling the return value to a different interval using multiplication or addition (a so-called affine transformation) might result in a bias in the resulting value as floats are not equally dense across the number line. As not all values can be exactly represented by a float, the result of the affine transformation might also result in values outside of the requested interval.
Use Random\Randomizer::getFloat() to generate a random float within an arbitrary interval. Use Random\Randomizer::getInt() to generate a random integer within an arbitrary interval.
Parameters
This function has no parameters.
Return Values
A pseudo random float value between 0.0 and 1.0, inclusive.
See Also
- Random\Randomizer::getFloat() - Get a uniformly selected float
- Random\Randomizer::getInt() - Get a uniformly selected integer
- random_int() - Get a cryptographically secure, uniformly selected integer
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User Contributed Notes 3 notes
rok kralj gmail com ¶
17 years ago
daniel dot baulig at gmx dot de ¶
14 years ago
Choose your weapon:
<?php
function mt_randf($min, $max)
{
return $min + abs($max - $min) * mt_rand(0, mt_getrandmax())/mt_getrandmax();
}
function lcg_randf($min, $max)
{
return $min + lcg_value() * abs($max - $min);
}
function randf($min, $max)
{
return $min + rand(0,getrandmax()) / getrandmax() * abs($max - $min);
}?>
