Description:
------------
i am trying to use v8js but it is not responding. 


<?php

class V8Js
{
    /* Constants */

    const V8_VERSION = '';

    const FLAG_NONE = 1;
    const FLAG_FORCE_ARRAY = 2;
    const FLAG_PROPAGATE_PHP_EXCEPTIONS = 4;

    /* Methods */

    /**
     * Initializes and starts V8 engine and returns new V8Js object with it's own V8 context.
     * Snapshots are supported by V8 4.3.7 and higher.
     * @param string $object_name
     * @param array $variables
     * @param array $extensions
     * @param bool $report_uncaught_exceptions
     * @param string $snapshot_blob
     */
    public function __construct($object_name = "PHP", array $variables = [], array $extensions = [], $report_uncaught_exceptions = TRUE, $snapshot_blob = NULL)
    {}

    /**
     * Provide a function or method to be used to load required modules. This can be any valid PHP callable.
     * The loader function will receive the normalised module path and should return Javascript code to be executed.
     * @param callable $loader
     */
    public function setModuleLoader(callable $loader)
    {}

    /**
     * Provide a function or method to be used to normalise module paths. This can be any valid PHP callable.
     * This can be used in combination with setModuleLoader to influence normalisation of the module path (which
     * is normally done by V8Js itself but can be overriden this way).
     * The normaliser function will receive the base path of the current module (if any; otherwise an empty string)
     * and the literate string provided to the require method and should return an array of two strings (the new
     * module base path as well as the normalised name).  Both are joined by a '/' and then passed on to the
     * module loader (unless the module was cached before).
     * @param callable $normaliser
     */
    public function setModuleNormaliser(callable $normaliser)
    {}

    /**
     * Compiles and executes script in object's context with optional identifier string.
     * A time limit (milliseconds) and/or memory limit (bytes) can be provided to restrict execution. These options will throw a V8JsTimeLimitException or V8JsMemoryLimitException.
     * @param string $script
     * @param string $identifier
     * @param int $flags
     * @param int $time_limit in milliseconds
     * @param int $memory_limit in bytes
     * @return mixed
     */
    public function executeString($script, $identifier = '', $flags = V8Js::FLAG_NONE, $time_limit = 0, $memory_limit = 0)
    {}

    /**
     * Compiles a script in object's context with optional identifier string.
     * @param $script
     * @param string $identifier
     * @return resource
     */
    public function compileString($script, $identifier = '')
    {}

    /**
     * Executes a precompiled script in object's context.
     * A time limit (milliseconds) and/or memory limit (bytes) can be provided to restrict execution. These options will throw a V8JsTimeLimitException or V8JsMemoryLimitException.
     * @param resource $script
     * @param int $flags
     * @param int $time_limit
     * @param int $memory_limit
     */
    public function executeScript($script, $flags = V8Js::FLAG_NONE, $time_limit = 0 , $memory_limit = 0)
    {}

    /**
     * Set the time limit (in milliseconds) for this V8Js object
     * works similar to the set_time_limit php
     * @param int $limit
     */
    public function setTimeLimit($limit)
    {}

    /**
     * Set the memory limit (in bytes) for this V8Js object
     * @param int $limit
     */
    public function setMemoryLimit($limit)
    {}

    /**
     * Set the average object size (in bytes) for this V8Js object.
     * V8's "amount of external memory" is adjusted by this value for every exported object.  V8 triggers a garbage collection once this totals to 192 MB.
     * @param int $average_object_size
     */
    public function setAverageObjectSize($average_object_size)
    {}

    /**
     * Returns uncaught pending exception or null if there is no pending exception.
     * @return V8JsScriptException|null
     */
    public function getPendingException()
    {}

    /**
     * Clears the uncaught pending exception
     */
    public function clearPendingException()
    {}

    /** Static methods **/

    /**
     * Registers persistent context independent global Javascript extension.
     * NOTE! These extensions exist until PHP is shutdown and they need to be registered before V8 is initialized.
     * For best performance V8 is initialized only once per process thus this call has to be done before any V8Js objects are created!
     * @param string $extension_name
     * @param string $code
     * @param array $dependencies
     * @param bool $auto_enable
     * @return bool
     */
    public static function registerExtension($extension_name, $code, array $dependencies, $auto_enable = FALSE)
    {}

    /**
     * Returns extensions successfully registered with V8Js::registerExtension().
     * @return array|string[]
     */
    public static function getExtensions()
    {}

    /**
     * Creates a custom V8 heap snapshot with the provided JavaScript source embedded.
     * Snapshots are supported by V8 4.3.7 and higher.  For older versions of V8 this
     * extension doesn't provide this method.
     * @param string $embed_source
     * @return string|false
     */
    public static function createSnapshot($embed_source)
    {}
}

final class V8JsScriptException extends Exception
{
    /**
     * @return string
     */
    final public function getJsFileName( ) {}

    /**
     * @return int
     */
    final public function getJsLineNumber( ) {}
    /**
     * @return int
     */
    final public function getJsStartColumn( ) {}
    /**
     * @return int
     */
    final public function getJsEndColumn( ) {}

    /**
     * @return string
     */
    final public function getJsSourceLine( ) {}
    /**
     * @return string
     */
    final public function getJsTrace( ) {}
}

final class V8JsTimeLimitException extends Exception
{
}

final class V8JsMemoryLimitException extends Exception
{
}
$v8 = new V8Js();
$v8->executeString("print('hello world');");
?>

Test script:
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not responding and i don't know my extensions are working perfectly