make-hex-keys.php

<?php

if (php_sapi_name() !== 'cli') {
  die('This script may only be run from the command line.' . "\n");
}

if ($argc < 2) {
  die('Usage: ' . $argv[0] . ' <encryption key>' . "\n");
}

$key = substr(str_pad($argv[1], 16, "\0"), 0, 16);
$iv = substr(md5($key), 0, 8);

printf("key bin\t== %s\nkey hex\t== %s\n", $key, strtoupper(bin2hex($key)));
printf("iv bin\t== %s\niv hex\t== %s\n", $iv, strtoupper(bin2hex($iv)));