Flyspray is an easy to use bug tracking system for those who don't require all the complexities of something like Bugzilla. It supports multiple projects and users, file attachments, and Instant Messaging (Jabber) notifications.

This software is created for small web projects, for teams who will work directly with client and need his feedback about the status of the project. It also can be used as a small BUG TRACKING system. And it can be defined by ADMIN several users who will be part of the project.

The BugPort system is an open-source, freely available, web-based system to manage tasks and defects throughout the software development process. BugPort is written with the PHP language using its object-oriented capabilities and is in use by INCOGEN for internal management of software development and QA.

Give your clients a Bug Tracking system which allows them to submit bugs to you without having to send multiple emails and spreadsheets. Bugalyzer is the ultimate Bug Tracker.

Mantis is a PHP/MySQL-driven web based bugtracking system. It is simpler than bugzilla and easily editable. The software resides on a webserver while any web browser should be able to function as a client. It supports multiple projects and email notification. Supports over 18 languages.

paBugs is a bug tracker designed to help developers organize bugs in their programs/scripts. It has an easy to use interface making browsing the database simple and a full featured easy to use admin center for managing the bug database. Written in PHP and using MySQL for the data backend, paBugs is a fast, server/CPU-friendly script. Main features include: Categories and Subcategories, Multiple Admin usernames, Admin Center, Admins can choose to receive e-mail notification when a new bug is reported, Anybody can report bugs, Reported bugs will not appear in the database until an admin approves it, Search database, and more.

phpBugTracker is meant to be a replacement for Bugzilla. This project grew out of the frustrations the author experienced in installing and using bugzilla. Those frustrations inspired the design goals: Simplicity in use and installation, Use templates to achieve presentation independence, and Use a database abstraction layer to achieve database independence.

Defect Tracking System is a PHP-based project designed to create a simple and easy to use bug/defect tracking system for multiple projects.