create_guid.php

function create_guid() {
	$random_bytes = '';

	if (function_exists('mcrypt_create_iv')) {
		$random_bytes .= @mcrypt_create_iv(100, MCRYPT_DEV_URANDOM);
	}
	
	if (strtoupper(substr(PHP_OS, 0, 3)) !== 'WIN') { // Unix
		if ($fp = @fopen('/dev/urandom','rb')) {
			$random_bytes .= @fread($fp, 100);
			@fclose($fp);
		}
	
		// (openssl_random_pseudo_bytes is very slow on Windows)
		if (function_exists('openssl_random_pseudo_bytes')) $random_bytes .= openssl_random_pseudo_bytes(100);
	}
	
	$random_bytes .= mt_rand() . uniqid(mt_rand(), true) . microtime() . lcg_value() . getmypid() . memory_get_usage() . serialize($_SERVER);
	
	return hash('sha256', $random_bytes);
}