Usage sample:
if (V8Js::registerExtension('myjs', 'var x = 1 + 1;', array(), true) === false) {
exit("Failed to register js extension script");
}
$v8js = new V8Js;
$jsExec = <<<EOD
x;
EOD;
echo $v8js->executeString($jsExec)."\n"; // print "2"