Simple PHP script to generate /etc/shadow style $6$ (SHA-512) password hashes

genshadow.php

#!/usr/bin/env php
<?php

if (count($argv) < 3) {
    echo <<<USAGE
Usage: genshadow.php salt password

USAGE;
    exit(0);
}

$salt = $argv[1];
$password = $argv[2];

echo crypt($password, "\$6\$$salt\$"), "\n";