Piwigo

Piwigo is a mature, open‑source photo gallery engine written primarily in PHP 7+. It exposes a REST‑like API for image metadata, album management, and user permissions while keeping the core logic in a modular MVC architecture. The application is designed to serve high‑volume photo collections, supporting tens of thousands of images per gallery without significant performance degradation. Internally it leverages MySQL 5+ / MariaDB for relational storage of albums, tags, and user roles, while optional ImageMagick or the PHP GD library handles on‑the‑fly image processing, thumbnails, and format conversions.

• Core framework – A lightweight MVC core with a plugin hook system that mirrors the functionality of popular CMSs. The core handles routing, authentication, and database abstraction via PDO.
• Database – MySQL or MariaDB is required; the schema includes tables for users, groups, albums, photos, tags, and plugin metadata. Indexes on foreign keys and tag columns keep lookup times low.
• Image processing – ImageMagick is preferred for speed and quality, but PHP GD serves as a fallback. Piwigo can generate multiple thumbnail sizes on demand and store them in the filesystem or an object storage backend.
• Cache – Optional integration with Memcached or Redis for caching album trees and image metadata, reducing database load under heavy traffic.

• Album hierarchy – Recursive album structures with customizable permissions (public, private, group‑based). The API exposes endpoints to create, move, and delete albums programmatically.
• Batch operations – Bulk upload, tagging, and deletion via the web UI or API. This is useful for migrating large collections.
• Extensible plugin system – Plugins can hook into events (onPhotoUpload, onAlbumCreate) and expose new endpoints or modify responses. Themes are separate packages that override templates without touching core code.
• Webhooks – Optional webhook support allows external services to react to events such as new photo uploads or album changes.
• Authentication – Supports native login, LDAP integration, and OAuth providers through plugins.

Piwigo is a classic LAMP stack application: Apache or nginx with PHP-FPM. It runs on any server that satisfies the PHP and database requirements, making it ideal for shared hosting or VPS deployments. For high‑availability scenarios, Docker images are available in the community repository; a typical stack includes nginx, php-fpm, mysql, and an optional redis container. Horizontal scaling is achieved by load‑balancing the web tier while sharing a common database and file store (e.g., NFS, S3-compatible object storage). The application’s statelessness (aside from the database) simplifies scaling.

Developers can extend Piwigo through its robust plugin API. A plugin declares hooks in a manifest file, and the core loads them automatically on boot. Themes are PHP/HTML templates that can be overridden per site, allowing UI customization without core edits. For deeper integration, the built‑in REST API (JSON) can be consumed by external applications—mobile clients, CMSs, or custom dashboards. Webhooks provide outbound event notifications to CI/CD pipelines or analytics services.

The codebase follows PSR‑4 autoloading and is well documented on GitHub, with a dedicated CONTRIBUTING.md guide. The community is active; the forums and wiki provide quick answers to integration questions. Licensing under GPLv2 encourages reuse, but developers can fork and modify the code without fear of licensing conflicts. Continuous integration pipelines ensure that new releases remain stable, and semantic versioning aids dependency management.

• Enterprise photo archives – Companies that need to store and share large media libraries can rely on Piwigo’s efficient indexing and permission system.
• Photographers’ portfolios – The theme/plugin ecosystem allows for custom branding while keeping the core lightweight.
• Educational institutions – Schools can host student photo projects with group‑based access control and bulk upload capabilities.
• Event management – Organizers can create temporary galleries with public access, then archive them automatically via plugins.

• Performance – Optimized queries and optional caching keep load times low even with hundreds of thousands of images.
• Flexibility – A pure PHP application that runs on any LAMP stack, with optional Docker support for rapid deployment.
• Extensibility – A mature plugin architecture lets developers add custom workflows, third‑party integrations, or new UI components.
• Longevity – Over 23 years of active development and a stable release cycle reduce maintenance overhead.
• Open source freedom – GPLv2 licensing allows full control over the code, encouraging custom modifications and internal audits.

Piwigo’s blend of a solid PHP foundation, scalable architecture, and developer‑friendly extensibility makes it an attractive choice for teams that require a high‑volume, self‑hosted photo gallery solution.