hash-cost-benchmark.php

<?php

/**
 * hash_cost_benchmark
 *
 * Benchmarks your server and selects an appropriate cost for hash_pasword
 *
 * @param float $target Maximum acceptable duration in seconds
 * @param int $cost Initial cost
 *
 * @return int Highest cost that can be used to meet the target
 */

public static function hash_cost_benchmark($target = 0.5, $cost = 8) {

    if (function_exists('password_hash')) {

        do {
            $cost++;
            $start = microtime(true);
            password_hash('test', PASSWORD_BCRYPT, ['cost' => $cost]);
            $end = microtime(true);
        } while (($end - $start) < $target);

        return $cost;

    } else {
        return 'Requires PHP >5.5';
    }

}