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Overview

The ipMoodle Dockerfile is built on php:8.2-fpm-alpine and includes essential PHP extensions for Moodle. You can extend this base image to add custom PHP extensions required for specific Moodle plugins or integrations.

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Understanding the Extension Installation Pattern

The Dockerfile (source/Dockerfile:1-39) follows a three-step pattern for installing PHP extensions:
1

Install system dependencies

Add required development libraries using apk add --no-cache
2

Configure extensions (if needed)

Some extensions like GD require configuration before compilation
3

Install PHP extensions

Use docker-php-ext-install to compile and enable extensions

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Currently Installed Extensions

The base ipMoodle image includes these extensions:
  • intl - Internationalization support
  • soap - SOAP protocol support
  • zip - ZIP archive handling
  • pgsql - PostgreSQL database driver
  • pdo_pgsql - PDO driver for PostgreSQL
  • exif - Image metadata reading
  • opcache - PHP opcode caching
  • bcmath - Arbitrary precision mathematics
  • sockets - Socket communication
  • mbstring - Multibyte string handling
  • sodium - Modern cryptography
  • gd - Image processing (with FreeType and JPEG support)

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Adding a Simple PHP Extension

For extensions that don’t require external dependencies:
1

Edit the Dockerfile

Open source/Dockerfile and locate the extension installation block (line 26-27):
RUN docker-php-ext-install -j$(nproc) \
    intl soap zip pgsql pdo_pgsql exif opcache bcmath sockets mbstring sodium
2

Add your extension

Append your extension name to the list:
RUN docker-php-ext-install -j$(nproc) \
    intl soap zip pgsql pdo_pgsql exif opcache bcmath sockets mbstring sodium pcntl
3

Rebuild the container

docker-compose down
docker-compose build --no-cache app
docker-compose up -d
The -j$(nproc) flag enables parallel compilation using all available CPU cores, speeding up the build process.

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Adding Extensions with Dependencies

Extensions requiring system libraries need a two-step process:

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Example: Adding LDAP Extension

1

Add system dependencies

Edit the dependency installation block (line 4-19):
RUN apk add --no-cache \
    git \
    linux-headers \
    oniguruma-dev \
    libsodium-dev \
    icu-dev \
    libpng-dev \
    libjpeg-turbo-dev \
    freetype-dev \
    libzip-dev \
    libxml2-dev \
    postgresql-dev \
    zlib-dev \
    shadow \
    ghostscript \
    dcron \
    openldap-dev  # Add this line
2

Add the PHP extension

RUN docker-php-ext-install -j$(nproc) \
    intl soap zip pgsql pdo_pgsql exif opcache bcmath sockets mbstring sodium ldap
3

Rebuild and verify

docker-compose build --no-cache app
docker-compose up -d
docker exec moodle_app php -m | grep ldap

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Adding Extensions Requiring Configuration

Some extensions need configuration before installation, similar to GD (line 22-23):

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Example: Adding IMAP Extension

# Install dependencies
RUN apk add --no-cache \
    imap-dev \
    openssl-dev \
    krb5-dev

# Configure and install
RUN docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
    && docker-php-ext-install -j$(nproc) imap

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Installing PECL Extensions

For extensions not bundled with PHP, use PECL:

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Example: Adding Redis Extension

1

Install build dependencies

RUN apk add --no-cache --virtual .build-deps \
    $PHPIZE_DEPS \
    autoconf \
    g++ \
    make
2

Install the PECL extension

RUN pecl install redis \
    && docker-php-ext-enable redis
3

Clean up build dependencies

RUN apk del .build-deps

RUN apk add --no-cache --virtual .build-deps \
        $PHPIZE_DEPS \
        autoconf \
        g++ \
        make \
    && pecl install redis \
    && docker-php-ext-enable redis \
    && apk del .build-deps

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Verifying Installed Extensions

After rebuilding, verify your extensions are loaded: 
# List all enabled extensions
docker exec moodle_app php -m

# Check specific extension
docker exec moodle_app php -m | grep redis

# View extension configuration
docker exec moodle_app php -i | grep -A 5 "redis"

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Configuring Extension Settings

Add extension-specific settings to the PHP configuration (line 30-36): 
RUN { \
    echo 'max_input_vars=5000'; \
    echo 'memory_limit=512M'; \
    echo 'upload_max_filesize=512M'; \
    echo 'post_max_size=512M'; \
    echo 'max_execution_time=600'; \
    echo 'opcache.enable=1'; \
    echo 'opcache.memory_consumption=128'; \
    echo 'redis.session.locking_enabled=1'; \
} > /usr/local/etc/php/conf.d/moodle.ini
Always rebuild with --no-cache flag when modifying the Dockerfile to ensure changes are applied:
docker-compose build --no-cache app

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Common Moodle Extensions

Depending on your Moodle plugins, you may need:
ExtensionUse CaseDependencies
ldapLDAP authenticationopenldap-dev
imapEmail integrationimap-dev openssl-dev krb5-dev
redisSession/cache storagePECL extension
imagickAdvanced image processingimagemagick-dev
xslXML transformationslibxslt-dev
curlHTTP requestsUsually included
ftpFTP repository supportNone

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Troubleshooting

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Extension fails to compile

Ensure all required -dev packages are installed in the Alpine dependency block. Search for the extension name + “alpine linux” to find required packages.
Always use --no-cache when testing new extensions:
docker-compose build --no-cache app
Check the PHP error log:
docker logs moodle_app

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Extension loads but Moodle doesn’t recognize it

  1. Verify the extension is enabled: 
    docker exec moodle_app php -m | grep your_extension
  2. Restart the PHP-FPM service: 
    docker-compose restart app
  3. Clear Moodle caches from Site administration > Development > Purge all caches
Some Moodle plugins check for specific PHP extensions during installation. Always verify extension requirements before installing plugins.

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