Generating "Very Strong" Plesk passwords

PasswordGenerator.php

<?php

function generatePassword($stronger = true) {
  $password = "";
  $length   = $stronger ? 16 : 8;
  $sets     = array(
    'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
    'abcdefghijklmnopqrstuvwxyz',
    '0123456789',
    '!@#$%^&*?_~',
  );

  // The minimum requirements of a "Very Strong" password 
  $types = [0, 0, 1, 1, 2, 2, 3];

  foreach ($types AS $type) {
    $randIdx = floor(strlen($sets[$type]) * lcg_value());
    $password .= substr($sets[$type], $randIdx, 1);
  }

  // Padd out the length of password string
  for ($i = strlen($password); $i < $length; $i++) {
    $typeIdx = floor(count($sets) * lcg_value());
    $charIdx = floor(strlen($sets[$typeIdx]) * lcg_value());
    $password .= substr($sets[$typeIdx], $charIdx, 1);
  }

  // Shuffle things up a bit
  return str_shuffle($password);
}

rather-crude-tests.php

<?php

$n = 10000;
echo "Checking $n passwords meet strength requirements\n";

for ($i = 0; $i < $n; $i++) {
  $pw = generatePassword();
  if (
       strlen($pw) < 16
    || preg_match_all("/[A-Z]/", $pw)  < 2
    || preg_match_all("/[a-z]/", $pw)  < 2
    || preg_match_all("/[0-9]/", $pw)  < 2
    || preg_match_all("/[!@#$%^&*?_~]/", $pw)  < 1
  ) {
    echo "FAILED! - ", $pw, "\n";
  }
}

echo "\n  ! Done";