Random string generator

random.php

<?php
/**
 * The random string generator helper
 *
 * Solution implemented from http://stackoverflow.com/a/13733588/1056679
 * 
 * Usage: CLI: php random.php {length}
 * length - length of the random string to generage
 *
 * @since   1.0.0
 * @package Randomness
 */
namespace Randomness;

/**
 * Class Random Generator
 *
 * Generates random alphanumeric characters.
 */
class Random_Generator {

  /**
   * Generate random string of specified length
   *
   * @param  int $length Length of the string.
   * @return string         Radnom string.
   */
  public function generate( int $length ) : string {
    $token  = '';
    $length = abs( $length );

    for ( $i = 0; $i < $length; $i++ ) {
        $random_key = $this->get_random_integer( 0, $this->get_alphabet_length() );
        $token     .= $this->get_alphabet()[ $random_key ];
    }

    return $token;
  }

  /**
   * Get the default alphabet
   *
   * @return string String of all the allowed characters.
   */
  private function get_alphabet() : string {
    return implode( range( 'a', 'z' ) )
        . implode( range( 'A', 'Z' ) )
        . implode( range( 0, 9 ) );
  }

  /**
   * Get length of the default alphabet
   *
   * @return int The length of the alphabet.
   */
  private function get_alphabet_length() : int {
    return strlen( $this->get_alphabet() );
  }

  /**
   * Get random integer in the given range
   *
   * @param  int $min Min value for the random integer range.
   * @param  int $max Max value for the random integer range.
   * @return int      Random integer
   */
  private function get_random_integer( int $min, int $max ) : int {
    $range = ( $max - $min );

    $log = log( $range, 2 );

    // Length in bytes.
    $bytes = (int) ( $log / 8 ) + 1;

    // Length in bits.
    $bits = (int) $log + 1;

    // Set all lower bits to 1.
    $filter = (int) ( 1 << $bits ) - 1;

    do {
      $rnd = hexdec( bin2hex( openssl_random_pseudo_bytes( $bytes ) ) );
      $rnd = $rnd & $filter;
    } while ( $rnd >= $range );

    return ( $min + $rnd );
  }
}

$random = new Random_Generator();

if (php_sapi_name() == "cli") {
  echo $random->generate( $argv[1] ), "\n";
} else {
  echo $random->generate( $_GET['len'] );
}