# A better PHP backtrace

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To get the backtrace in PHP you can use the `debug_backtrace` function. By default, it can be hard to work with. The
reported function name for a frame is skewed: it belongs to the previous frame. Also, options need to be passed using a bitmask.

This package provides a better way than `debug_backtrace` to work with a back trace. Here's an example:

```php
// returns an array with `Spatie\Backtrace\Frame` instances
$frames = Spatie\Backtrace\Backtrace::create()->frames(); 

$firstFrame = $frames[0];

$firstFrame->file; // returns the file name
$firstFrame->lineNumber; // returns the line number
$firstFrame->class; // returns the class name
```

## Support us

[<img src="https://github-ads.s3.eu-central-1.amazonaws.com/backtrace.jpg?t=1" width="419px" />](https://spatie.be/github-ad-click/backtrace)

We invest a lot of resources into creating [best in class open source packages](https://spatie.be/open-source). You can
support us by [buying one of our paid products](https://spatie.be/open-source/support-us).

We highly appreciate you sending us a postcard from your hometown, mentioning which of our package(s) you are using.
You'll find our address on [our contact page](https://spatie.be/about-us). We publish all received postcards
on [our virtual postcard wall](https://spatie.be/open-source/postcards).

## Installation

You can install the package via composer:

```bash
composer require spatie/backtrace
```

## Usage

This is how you can create a backtrace instance:

```php
$backtrace = Spatie\Backtrace\Backtrace::create();
```

### Getting the frames

To get all the frames you can call `frames`.

```php
$frames = $backtrace->frames(); // contains an array with `Spatie\Backtrace\Frame` instances
```

A `Spatie\Backtrace\Frame` has these properties:

- `file`: the name of the file
- `lineNumber`: the line number
- `arguments`: the arguments used for this frame. Will be `null` if `withArguments` was not used.
- `class`: the class name for this frame. Will be `null` if the frame concerns a function.
- `method`: the method used in this frame
- `object`: the object when the frame is in an object context (method call, closure bound to object, arrow function which captured `$this`, etc.). Will be `null` if `withObject` was not used.
- `applicationFrame`: contains `true` is this frame belongs to your application, and `false` if it belongs to a file in
  the vendor directory. A couple edge cases exist, see "application frames" below.

### Collecting arguments and objects

For performance reasons, the frames of the back trace will not contain the arguments of the called functions and the
object. If you want to add those, use the `withArguments` and `withObject` methods.

```php
$backtrace = Spatie\Backtrace\Backtrace::create()->withArguments()->withObject();
```

#### Reducing arguments

For viewing purposes, arguments can be reduced to a string:

```php
$backtrace = Spatie\Backtrace\Backtrace::create()->withArguments()->reduceArguments();
```

By default, some typical types will be reduced to a string. You can define your own reduction algorithm per type by implementing an `ArgumentReducer`:

```php
class DateTimeWithOtherFormatArgumentReducer implements ArgumentReducer
{
    public function execute($argument): ReducedArgumentContract
    {
        if (! $argument instanceof DateTimeInterface) {
            return UnReducedArgument::create();
        }

        return new ReducedArgument(
            $argument->format('d/m/y H:i'),
            get_class($argument),
        );
    }
}
```

This is a copy of the built-in argument reducer for `DateTimeInterface` where we've updated the format. An `UnReducedArgument` object is returned when the argument is not of the expected type. A `ReducedArgument` object is returned with the reduced value of the argument and the original type of the argument.

The reducer can be used as such:

```php
$backtrace = Spatie\Backtrace\Backtrace::create()->withArguments()->reduceArguments(
    Spatie\Backtrace\Arguments\ArgumentReducers::default([
        new DateTimeWithOtherFormatArgumentReducer()
    ])
);
```

Which will first execute the new reducer and then the default ones.

### Setting the application path

You can use the `applicationPath` to pass the base path of your app. This value will be used to determine whether a
frame is an application frame, or a vendor frame. Here's an example using a Laravel specific function.

```php
$backtrace = Spatie\Backtrace\Backtrace::create()->applicationPath(base_path());
```
### Removing the application path from the file name

You can use `trimFilePaths` to remove the base path of your app from the file. This will only work if you use it in conjunction with the `applicationPath` method re above. Here's an example using a Laravel specific function. This will ensure the Frame has the trimmedFilePath property set.

```php
$backtrace = Backtrace::create()->applicationPath(base_path())->trimFilePaths());
```

### Application frames

By default, a frame is considered an application frame when the file of the frame is not in the vendor directory. The following edge cases apply:

- Laravel's `artisan` CLI file (generally found in the root of the project) is considered a vendor file and frame
- Statamic's `please` CLI file (generally found in the root of the project) is considered a vendor file and frame

### Getting a certain part of a trace

If you only want to have the frames starting from a particular frame in the backtrace you can use
the `startingFromFrame` method:

```php
use Spatie\Backtrace\Backtrace;
use Spatie\Backtrace\Frame;

$frames = Backtrace::create()
    ->startingFromFrame(function (Frame $frame) {
        return $frame->class === MyClass::class;
    })
    ->frames();
```

With this code, all frames before the frame that concerns `MyClass` will have been filtered out.

Alternatively, you can use the `offset` method, which will skip the given number of frames. In this example the first 2 frames will not end up in `$frames`.

```php
$frames = Spatie\Backtrace\Backtrace::create()
    ->offset(2)
    ->frames();
```

### Limiting the number of frames

To only get a specific number of frames use the `limit` function. In this example, we'll only get the first two frames.

```php
$frames = Spatie\Backtrace\Backtrace::create()
    ->limit(2)
    ->frames();
```

###  Getting a backtrace for a throwable

Here's how you can get a backtrace for a throwable.

```php
$frames = Spatie\Backtrace\Backtrace::createForThrowable($throwable)
```

Because we will use the backtrace that is already available in the throwable, the frames will contain the arguments used
in the backtrace as long as the `zend.exception_ignore_args` INI option is disabled (set to `0`) *before* the throwable
is thrown. On the other hand, objects will never be included in the backtrace. 
[More information](https://www.php.net/manual/en/throwable.gettrace.php#129087).

## Testing

``` bash
composer test
```

## Changelog

Please see [CHANGELOG](CHANGELOG.md) for more information on what has changed recently.

## Contributing

Please see [CONTRIBUTING](https://github.com/spatie/.github/blob/main/CONTRIBUTING.md) for details.

## Security Vulnerabilities

Please review [our security policy](../../security/policy) on how to report security vulnerabilities.

## Credits

- [Freek Van de Herten](https://github.com/freekmurze)
- [All Contributors](../../contributors)

## License

The MIT License (MIT). Please see [License File](LICENSE.md) for more information.
