PHP Memoization

memoization.php

<?php

function args_to_key($args) {
    $tmp = array();
    $it = new RecursiveIteratorIterator(new RecursiveArrayIterator($args));
    foreach($it as $v) {
        if (is_object($v)) {
            $tmp[] = spl_object_hash($v);
        } elseif (is_scalar($v)) {
            $tmp[] = $v;
        }
    }
    return md5(implode('', $tmp));
}

function __memoize($func) {
    $_func = function() use ($func) {
        static $cache = array();
        $args = func_get_args();
        $key = args_to_key($args);
        if (array_key_exists($key, $cache)) {
            return $cache[$key];
        }
        $ret = call_user_func_array($func, $args);
        $cache[$key] = $ret;
        return $cache[$key];
    };
    return $_func;
}

function slow($a, $b) {
    sleep(1);
    return mt_rand(1, 1000);
}

echo "Calling slow(1, 2): ";
$start = microtime(true);
echo slow(1, 2) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "Calling slow(1, 2): ";
$start = microtime(true);
echo slow(1, 2) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "\n\nMemoizing it\n\n";

$slow = __memoize('slow');
echo "Calling slow(1, 2): ";
$start = microtime(true);
echo $slow(1, 2) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "Calling slow(1, 2): ";
$start = microtime(true);
echo $slow(1, 2) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "Calling slow(3, 4): ";
$start = microtime(true);
echo $slow(3, 4) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "Calling slow(3, 4): ";
$start = microtime(true);
echo $slow(3, 4) . "\n";
printf("Took: %.4f seconds\n", microtime(true) - $start);

echo "\n\n";