If you want the output of the JS code not to be printed in the output and have it in PHP:
<?php
// Create a new V8Js object
$v8 = new V8Js();
// Define a JavaScript function
$JS = <<<EOT
(function() {
return 'Hello World!';
})();
EOT;
// Execute the JavaScript function using V8js
$result = $v8->executeString($JS);
// Output the result
var_dump($result);
?>
Output:
string(12) "Hello World!"