Docker-php-ext-install mcrypt missing folder - php

Question

I try to install mcrypt in my docker image based on php:7.2-apache. Therefore I use the RUN-Command from the documentation and also answerd here but I receive this error:
error: /usr/src/php/ext/mcrypt does not exist
usage: /usr/local/bin/docker-php-ext-install [-jN] ext-name [ext-name ...]
ie: /usr/local/bin/docker-php-ext-install gd mysqli
/usr/local/bin/docker-php-ext-install pdo pdo_mysql
/usr/local/bin/docker-php-ext-install -j5 gd mbstring mysqli pdo pdo_mysql shmop
if custom ./configure arguments are necessary, see docker-php-ext-configure
Possible values for ext-name:
bcmath bz2 calendar ctype curl dba dom enchant exif fileinfo filter ftp gd gettext gmp hash iconv imap interbase intl json ldap mbstring mysqli oci8 odbc opcache pcntl pdo pdo_dblib pdo_firebird pdo_mysql pdo_oci pdo_odbc pdo_pgsql pdo_sqlite pgsql phar posix pspell readline recode reflection session shmop simplexml snmp soap sockets sodium spl standard sysvmsg sysvsem sysvshm tidy tokenizer wddx xml xmlreader xmlrpc xmlwriter xsl zend_test zip
Some of the above modules are already compiled into PHP; please check
the output of "php -i" to see which modules are already loaded.
ERROR: Service 'web' failed to build: The command '/bin/sh -c apt-get update && apt-get install -y libfreetype6-dev libjpeg62-turbo-dev libmcrypt-dev libpng-dev && docker-php-ext-install -j$(nproc) iconv mcrypt gd mbstring zip' returned a non-zero code: 1
My Dockerfile:
FROM php:7.2-apache
RUN apt-get update && apt-get install -y \
libfreetype6-dev \
libjpeg62-turbo-dev \
libmcrypt-dev \
libpng-dev \
&& docker-php-ext-install -j$(nproc) iconv mcrypt gd mbstring zip
# && docker-php-ext-configure gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ \
# && docker-php-ext-install -j$(nproc) gd
COPY ./etc/000-default.conf /etc/apache2/sites-available/
EXPOSE 80
Has anybody an idea how to solve or how to get the needed files in the requested folder?
Thanks!

Answer 1

mcrypt extension is not provided with the PHP source since 7.2 , but are instead available through PECL. To install a PECL extension in docker, use pecl install to download and compile it, then use docker-php-ext-enable to enable it:
pecl install mcrypt-1.0.5
docker-php-ext-enable mcrypt
Before the pecl install you may need to install/update the package libmcrypt-dev
apt-get update && apt-get install -y libmcrypt-dev

Answer 2

Building on MoiioM's answer, this worked for me using the 7.2-stretch Docker image from PHP
RUN apt-get update && apt-get install -y libmcrypt-dev \
&& pecl install mcrypt-1.0.4 \
&& docker-php-ext-enable mcrypt

Answer 3

To install mcrypt extension you have to make sure you did install libmcrypt-dev which is required.
Try to add:
RUN apt install libmcrypt-dev
before you are trying to install extensions for php.
Update
Try to run first:
docker-php-ext-configure mcrypt
and then
docker-php-ext-install mcrypt