Methods abound for keeping track of what you should be working on. Formal issue tracking systems are a reliable way to keep lists of bugs, feature requests, and other work that needs to be done. These systems ensure that each task is assigned to a person responsible for it. Each task is associated with relevant metadata, such as priority, estimated length of time to do it, progress and completion status, and comments. This metadata makes it a breeze to sort, search, and understand the background of each issue.
There are lots of issue tracking systems out there, and, like with source control systems, which one you use may be dictated by whatever’s already in use in the project you’re joining or the company you work for. If you’re looking for a free system to try out, one worth mentioning is MantisBT, because it is open source and itself written in PHP.
Issue tracking systems are agnostic about what programming language you’re using, so no special work is required to get your PHP programs to play nicely with them. A helpful convention, though, is to refer to issue IDs liberally in your program when you’re writing code relevant to a particular issue.
Each issue tracked by the system gets an ID. It might be numbers, letters, or a combination, and it provides a short and unique way to reference an issue. For example, imagine a bug with the description “Login doesn’t work when there’s a + in email address” that, when entered into the system, gets assigned the ID MXH-26. When you write the code to fix the problem, reference that issue ID in a comment. For example:
// MXH-26: URL-encode email address to prevent problems with +
$email = urlencode($email);
This way, when another developer is looking at the code, she can see the issue number and look it up in the issue tracking system for context and an explanation of why your code is there.
Source: Sklar David (2016), Learning PHP: A Gentle Introduction to the Web’s Most Popular Language, O’Reilly Media; 1st edition.