Docker - 调用未定义的函数mcrypt_get_block_size（）

In docker I get Call to undefined function mcrypt_get_block_size(), in the container I installed php5-mcrypt and in the php.ini I writted extension=mcrypt.so but don't working it.

sudo docker exec -i -t docker_pbr_1 /bin/bash
apt-get update
apt-get install php5-mcrypt
php5enmod mcrypt
/etc/init.d/apache2 restart

I've PHP 5.6 but php5-mcrypt is not found.