guid.php

<?php

function formatGUID($chars, $uppercase = false, $braces = false, $hyphen = true)
{
	$c = $chars;
	$h = $hyphen ? '-' : '';
	$g = 
		"{$c[00]}{$c[01]}{$c[02]}{$c[03]}{$c[04]}{$c[05]}{$c[06]}{$c[07]}{$h}".
		"{$c[08]}{$c[09]}{$c[10]}{$c[11]}{$h}".
		"{$c[12]}{$c[13]}{$c[14]}{$c[15]}{$h}".
		"{$c[16]}{$c[17]}{$c[18]}{$c[19]}{$h}".
		"{$c[20]}{$c[21]}{$c[22]}{$c[23]}{$c[24]}{$c[25]}{$c[26]}{$c[27]}{$c[28]}{$c[29]}{$c[30]}{$c[31]}";

	$uppercase && $g = strtoupper($g);
	$braces    && $g = "\{$g\}";

	return $g;
}

function rand_1() { return md5(uniqid(rand(), true)); }
function rand_2() { return bin2hex(openssl_random_pseudo_bytes(16, $strong)); }
function rand_3()
{
	static $handle;

	if (!isset($handle)) {
		$handle = fopen('/dev/urandom', 'rb');
		if ($handle === false)
			return false;
	}

	return bin2hex(fread($handle, 16));
}

$iterations = isset($argv[1]) ? (int)$argv[1] : 10000;
$repeat     = isset($argv[2]) ? (int)$argv[2] : 1;
$loop       = 0;
$memorycap  = return_bytes(ini_get('memory_limit')) - 104857600; // max - 1MB

while (($repeat == -1 ? true : $repeat--) && ++$loop) {

	for ($num=1; $num<=3; $num++) {
		$func = "rand_{$num}";

		$st = microtime(true);

		for ($i=0; $i<$iterations; $i++) {
			$guid = formatGUID($func());

			if (isset($guids[$num][$guid]))
				trigger_error("Alogrithm #$num created a collision !", E_USER_NOTICE);
			else
				$guids[$num][$guid] = true;
		}
		
		$nd = microtime(true);
		$me = memory_get_usage();

		echo str_pad(get_bytes($me), 10, ' ', STR_PAD_LEFT) . " [$loop:$num] ", round(($nd - $st) * 1000000), "µs              \r";
	}

	if ($me >= $memorycap)
		unset($guids);
}

function return_bytes($val)
{
    $val = trim($val);
    $last = strtolower($val[strlen($val)-1]);
    switch($last) {
        // The 'G' modifier is available since PHP 5.1.0
        case 'g':
            $val *= 1024;
        case 'm':
            $val *= 1024;
        case 'k':
            $val *= 1024;
    }

    return $val;
}

function get_bytes($val)
{
	if ($val > 1000) {
		$val /= 1024;
		$unit = 'k';
	}

	if ($val > 1000) {
		$val /= 1024;
		$unit = 'm';
	}

	if ($val > 1000) {
		$val /= 1024;
		$unit = 'g';
	}

	return round($val,2).strtoupper($unit)."B";
}