# PHP Debugging (Xdebug)

**Xdebug** is an extension for PHP to assist with debugging and development. It upgrades PHP's native `var_dump()` function, adds stack traces for Notices, Warnings, Errors and Exceptions, and most importantly, enables **Step Debugging**.

---

## 1. Installation
Xdebug is a PHP extension that needs to be installed and enabled in your `php.ini` file.

```bash
# Linux (Ubuntu/Debian)
sudo apt-get install php-xdebug
```

## 2. Configuration (`php.ini`)
To enable step debugging, you typically add the following to your `php.ini` or `xdebug.ini`:

```ini
[xdebug]
zend_extension=xdebug
xdebug.mode=debug
xdebug.start_with_request=yes
xdebug.client_host=127.0.0.1
xdebug.client_port=9003
```

## 3. Step Debugging
Step debugging allows you to interactively walk through your code to see what is happening.
1.  **Set a Breakpoint:** In your IDE (like VS Code or PhpStorm), click next to a line number to set a red dot.
2.  **Listen for Connections:** Turn on the "Start Listening for PHP Debug Connections" button in your IDE.
3.  **Run Script:** Refresh your browser. The execution will pause at your breakpoint.

## 4. Better `var_dump()`
Without Xdebug, `var_dump()` output is plain text and hard to read for complex arrays. Xdebug formats it with HTML, colors, and collapsible limits.

```php
$arr = ['a' => 1, 'b' => [1, 2, 3]];
var_dump($arr);
// With Xdebug, this renders as a structured, colorful HTML table.
```

## 5. Profiling
Xdebug can also profile your PHP scripts to find bottlenecks.
*   Set `xdebug.mode=profile`.
*   It generates cachegrind files that can be viewed in tools like KCacheGrind or QCacheGrind.

[[programming/php/php]] [[programming/php/php-error-handling]]