Random\Randomizer::getBytesFromString

Description

Generates a string containing uniformly selected random bytes from the input string with the requested length.

The chance for a byte to be selected is proportional to its share of the input string. If each byte occurs the same amount of times, each byte is equally likely to be selected.

Parameters

string

The String from which the returned bytes are selected.

length

The length of the random String that should be returned in bytes; must be 1 or greater.

Return Values

A String containing the requested number of random bytes taken from the input string.

Errors/Exceptions

• If string is empty, a ValueError will be thrown.
• If the value of length is less than 1, a ValueError will be thrown.

Examples

Random\Randomizer::getBytesFromString example

<?php
$randomizer = new \Random\Randomizer();

printf(
    "%s.example.com",
    $randomizer->getBytesFromString('abcdefghijklmnopqrstuvwxyz0123456789', 16)
);
?>

The above example will output something similar to:

3zsw04eiubcf82jd.example.com

Generate a random code for multi-factor authentication

<?php
// The Secure engine is the default, but we make it explicit, because
// multi-factor codes are security sensitive.
$randomizer = new \Random\Randomizer(new \Random\Engine\Secure());

echo implode('-', str_split($randomizer->getBytesFromString('0123456789', 20), 5));
?>

The above example will output something similar to:

11551-80418-27047-42075

Select from a string with a non-uniform distribution

<?php
$randomizer = new \Random\Randomizer();

echo $randomizer->getBytesFromString('aaaaabcdef', 20);
?>

The above example will output something similar to:

fddacbeaaeaaacaaaaca

See Also

• Random\Randomizer::getBytes