Poor V8Function call performance

[stesie]

If you keep a reference to a JS function in a PHP variable (by means of a V8Function object) like so:

$v8 = new V8Js();
$func = $v8->executeString('(function() { print("Hello World\\n"); });');

for($i = 0; $i < 1000; $i ++) {
    $func();
}

... the performance is pretty bad: V8Js 0.2.1 takes 2.466s to execute these 1k calls, V8Js 0.1.5 even needs 80s.

Compared to the performance we achieve if executing the functions via executeString like

$v8 = new V8Js();
for($i = 0; $i < 1000; $i ++) {
    $v8->executeString('(function() { print("Hello World\\n"); })();');
}

... which even has the disadvantage that the function is compiled over and over again, it just takes 0.168s to run on recent V8Js and 0.247s on older ones.