我尝试通过此行运行控制台服务器：
php app/console server:run xxx.xxx.xxx.xxx:8000 --docroot=public_html
但是我给出了这个错误：
`Fatal error: Uncaught
Symfony\Component\Debug\Exception\UndefinedFunctionException: Attempted to call function "iconv" from namespace "Symfony\Polyfill\Mbstring". in /home/raghibkosh/public_html/enews/vendor/symfony/polyfill- mbstring/Mbstring.php:520
Stack trace:
#0 /home/raghibkosh/public_html/enews/vendor/symfony/polyfill-
mbstring/bootstrap.php(46): Symfony\Polyfill\Mbstring\Mbstring::mb_strwidth('
[Symfony\\Comp...', 'ASCII')
#1 /home/raghibkosh/public_html/enews/vendor/symfony/symfony/src/Symfony/Component/Console/Application.php(1106): mb_strwidth(' [Symfony\\Comp...', 'ASCII')
#2 /home/raghibkosh/public_html/enews/vendor/symfony/symfony/src/Symfony/Component/Console/Application.php(650): Symfony\Component\Console\Application->stringWidth(' [Symfony\\Comp...')
#3 /home/raghibkosh/public_html/enews/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/EventListener/DebugHandlersListener.php(105): Symfony\Component\Console\Application->renderException(Object(Symfony\Component\Debug\Exception\UndefinedFunctionExcep in /home/raghibkosh/public_html/enews/vendor/symfony/polyfill-mbstring/Mbstring.php on line 520`
PHP 7.0.32（cli）（内置：2018年10月5日15:45:03）（NTS）
Composer版本1.7.2 2018-08-16 16:57:12
CentOS Linux版本7.5.1804（核心）
如何解决此问题？