Use XDebug for PHP Project Debugging

XDebug is an indispensable debugging tool in PHP development, offering powerful features for breakpoint debugging, performance analysis, and code coverage. With XDebug, developers can set breakpoints in the code, inspect variable values, trace function call stacks, analyze performance bottlenecks, and greatly enhance PHP development efficiency and code quality.

XDebug Introduction

XDebug is a PHP extension designed to provide debugging and analysis capabilities. It allows developers to set breakpoints in the code, step through the code, inspect variable values and program states, helping them better understand and debug the code.

Enable Xdebug and Configure Debugging Environment

ServBay comes with XDebug pre-installed for each PHP version.

Note

Please refer to the article How to Enable ServBay's Built-in Xdebug Module for information on how to enable the Xdebug module and configure PHPStorm.

Specific Debugging Example

Sample Project Structure

Assuming we have a simple PHP project with the following directory structure:

servbay_xdebug_app/
├── src/
│   └── Calculator.php
└── index.php

The content of the Calculator.php file is as follows:

<?php
namespace App;

class Calculator
{
    public function add($a, $b)
    {
        return $a + $b;
    }

    public function subtract($a, $b)
    {
        return $a - $b;
    }
}

The content of the index.php file is as follows:

<?php
require 'vendor/autoload.php';

use App\Calculator;

$calculator = new Calculator();
$sum = $calculator->add(5, 3);
$difference = $calculator->subtract(5, 3);

echo "Sum: " . $sum . "\n";
echo "Difference: " . $difference . "\n";

Setting Breakpoints

We want to debug the add method in the Calculator class and see how it executes. Open the Calculator.php file in PHPStorm and set a breakpoint on the line return $a + $b;.

Starting the Debugging Session

1. In PHPStorm, click the Start Listening for PHP Debug Connections button (the little bug icon) on the top toolbar.
2. In the browser, access your PHP application, such as https://servbay-xdebug-app.test/index.php.

Debugging Process

1. When the browser accesses index.php, XDebug will automatically connect to PHPStorm and pause execution at the set breakpoint.
2. In PHPStorm, you'll see the code paused at the return $a + $b; line in the add method of the Calculator.php file.

Inspecting Variable Values

1. In PHPStorm's debug window, you can see the current executing code line, call stack, variable values, etc.
2. In the Variables panel, you can see the values of the variables $a and $b are 5 and 3, respectively.

Step Execution

1. Click the Step Over button (or press F8) to step through the code line by line.
2. Observe the changes in variable values to ensure the add method returns the correct result.

Resume Execution

1. Click the Resume Program button (or press F9) to continue executing the code.
2. The program will continue running until it hits the next breakpoint or finishes execution.

View Output

1. Check the output in the browser, which should display:

   Sum: 8
   Difference: 2

Conclusion

XDebug allows developers to easily set breakpoints, inspect variable values, and step through code in PHP, enabling them to better understand and debug code. In practical development, XDebug's breakpoint debugging feature can help developers quickly locate and resolve issues, improving development efficiency and code quality. Through the specific debugging example above, we can see the powerful features and convenience of XDebug in PHP project debugging.