php random password generator

passwordGenerator.php

<?php

function getRandomPassword($passwordLength = 4) {
  $alphabet = 'abcdefghijklmnopqrstuvwxyz';
  $characterCollection = array_merge(str_split($alphabet), str_split(strtoupper($alphabet)), str_split('1234567890'), str_split('!~@#-_+<>[]{}'));
  $randomPassword = '';

  for($i = 0; $i < $passwordLength; $i++) {
    $randomPassword .= $characterCollection[array_rand($characterCollection)];
  }

  return $randomPassword;
}


echo htmlspecialchars(getRandomPassword())   . '<hr/>';
echo htmlspecialchars(getRandomPassword(7)) . '<hr/>';
echo htmlspecialchars(getRandomPassword(100)) . '<hr/>';