Random\Randomizer
PHP Manual

Random\Randomizer::getBytesFromString

Get random bytes from a source string

Description

public string Random\Randomizer::getBytesFromString(string $string, int $length)

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.
  • Any Throwables thrown by the Random\Engine::generate method of the underlying Random\Randomizer::$engine.

Examples

Example #1 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

Example #2 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

Example #3 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