PHP Tail Recursion

gistfile1.aw

function tailrec($func)
{
	$acc = array();
	$recursing = FALSE;
	$func = new ReflectionFunction($func);

	return function() use ($func, &$acc, &$recursing) {

		$acc[] = func_get_args();

		if ( ! $recursing)
		{
			$recursing = TRUE;

			while ( ! empty($acc))
			{
				$ret = $func->invokeArgs(array_shift($acc));
			}

			$recursing = FALSE;
			return $ret;
		}
	};
}

// in order to recurse on a closure in php you need to
// pass a reference to the assigned variable.
$sumrand = tailrec(function($n, $sum) use (&$sumrand) {
	if ($n == 0)
	{
		return $sum;
	}
	
	return $sumrand($n - 1, $sum + rand(0, 1));
});

echo $sumrand(500000, 0) . "\n";

I optimized on your code to avoid the use(&$sumrand) part with a 5.4 only example:

https://gist.github.com/4145442