PHP Argon2 benchmark

## argon2_benchmark.php
<?php
/**
 * Password Argon2 Hash Benchmark
 * Argon2 is available since PHP 7.2
 *
 * Just upload this script to your server and run it, either through CLI or by calling it in your browser.
 *
 * See Argon2 specs https://password-hashing.net/argon2-specs.pdf chapter 9 Recommended Parameters
 */
// Upper time limit to check
$upperTimeLimit = 2500;

$threads = [1, 2, 4];

$time_cost_min = 1;
$time_cost_max = 8;

$memory_cost_min = 1 << 10; // 1 MB
$memory_cost_max = 1 << 18; // 256 MB

$password = 'this_is_just_a_long_string_to_test_on_U8WNZqmz8ZVBNiNTQR8r';

if (php_sapi_name() !== 'cli' ) echo "<pre>";
echo "\nPassword ARGON2 Benchmark";
echo "\nWill run until the upper limit of {$upperTimeLimit}ms is reached for each thread value";
echo "\n\nTimes are expressed in milliseconds.";

$start = microtime(true);
$hash = password_hash($password, PASSWORD_ARGON2I);
$time = round((microtime(true) - $start) * 1000);
echo "\n\n\nTime with default settings: {$time}ms";
echo "\nHash = $hash";

foreach($threads as $thread) {
    echo "\n\n\n=Testing with $thread threads";
    echo "\n m_cost (MB) ";
    for ($m_cost = $memory_cost_min; $m_cost <= $memory_cost_max; $m_cost *= 2) {
        $m_cost_mb = $m_cost / 1024;
        echo '|' . str_pad($m_cost_mb, 5, ' ', STR_PAD_BOTH);
    }
    echo "\n             =====================================================";
    for ($time_cost = $time_cost_min; $time_cost <= $time_cost_max; $time_cost++) {
        echo "\n t_cost=$time_cost    ";
        for ($m_cost = $memory_cost_min; $m_cost <= $memory_cost_max; $m_cost *= 2) {

            $start = microtime(true);
            password_hash($password, PASSWORD_ARGON2I, [
                'memory_cost' => $m_cost,
                'time_cost'   => $time_cost,
                'threads'     => $thread,
            ]);
            $time = round((microtime(true) - $start) * 1000);

            if ($time < $upperTimeLimit) {
                echo '|' . str_pad($time, 5, ' ', STR_PAD_BOTH);
            } else {
                echo '|' . str_pad(">LIM", 5, ' ', STR_PAD_BOTH);
                $m_cost = $memory_cost_max;
                $time_cost = $time_cost_max;
            }

        }
    }
}
echo "\n\n";

if (php_sapi_name() !== 'cli' ) echo "</pre>";