Grzegorz Drozd

2025-01-27

Breakpoint types in xdebug

When debugging PHP code, Xdebug serves as an essential tool for developers, enabling efficient identification and resolution of issues. Breakpoints are a critical feature of Xdebug, allowing you to pause the execution of your code at specific points and inspect the state of variables and processes. While the examples and screenshots in this article use PHPStorm, other IDEs offer similar features. This article explores the various types of breakpoints available in Xdebug: regular, conditional, non-suspending, function, and exception.

Regular Breakpoints

Regular breakpoints are the most straightforward type. They allow you to halt execution at a specific line of code. Developers typically use these to inspect variable states or understand the flow of execution at a particular point in the program.

Once the program execution reaches the breakpoint, Xdebug pauses the execution, allowing you to inspect the current state.

Conditional Breakpoints

Conditional breakpoints are an advanced type that allow execution to pause only when specific conditions are met. These conditions are logical expressions that evaluate to true.

Imagine debugging a loop that iterates hundreds of times. You’re interested only in the 10th iteration. By setting a conditional breakpoint, you can pause the execution when the loop counter equals 10. Or when $user->getId() == 10 or anything you need.

Non-Suspending Breakpoints

Non-suspending breakpoints are unique in that they do not halt the execution of your code. Instead, they allow you to log information or trigger a custom action whenever they are reached.

These are useful for scenarios where you want to log values or monitor execution flow without interrupting the runtime. For example, you might log database queries or track function calls.

Function Breakpoints

Function breakpoints let you pause execution whenever a specific function is called. These are especially useful for debugging function behavior across multiple files or tracking down unexpected calls. There’s no need to track all calls to a specific function or method manually; simply place a breakpoint on the function’s definition line, and Xdebug will automatically pause execution whenever the function is invoked.

Xdebug will pause execution whenever the specified function is called.

Exception Breakpoints

Exception breakpoints are designed to pause execution whenever a specific exception is thrown. They help you identify where exceptions occur and analyze the state of your application at that point.

Set the exception type in your IDE’s breakpoint configuration. In PHPStorm, go to the debugging tool window, press the “View Breakpoints” icon, and in the list of all breakpoints, press the plus icon over the tree on the left. From the list, select “Exception Breakpoint.”