public function checkExtension($extension)
    {
        // Check for HHVM and built-in extensions
        if ($this->php()->isHhvm()) {
            $this->extensions = [
                '_hhvm',
                'apache',
                'asio',
                'bcmath',
                'bz2',
                'ctype',
                'curl',
                'debugger',
                'fileinfo',
                'filter',
                'gd',
                'hash',
                'hh',
                'iconv',
                'icu',
                'imagick',
                'imap',
                'json',
                'mailparse',
                'mcrypt',
                'memcache',
                'memcached',
                'mysql',
                'odbc',
                'openssl',
                'pcre',
                'phar',
                'reflection',
                'session',
                'soap',
                'std',
                'stream',
                'thrift',
                'url',
                'wddx',
                'xdebug',
                'zip',
                'zlib',
            ];
        }

        // Get the PHP extensions available
        if (!$this->extensions) {
            $this->extensions = (array) $this->bash->run($this->php()->extensions(), false, true);
        }

        return in_array($extension, $this->extensions, true);
    }