---
Hoa is a modular, extensible and
structured set of PHP libraries.
Moreover, Hoa aims at being a bridge between industrial and research worlds.
# Hoa\Exception
[](https://webchat.freenode.net/?channels=#hoaproject)
[](https://gitter.im/hoaproject/central)
[](https://central.hoa-project.net/Documentation/Library/Exception)
[](https://waffle.io/hoaproject/exception)
This library allows to use advanced exceptions. It provides generic exceptions
(that are sent over the `hoa://Event/Exception` event channel), idle exceptions
(that are not sent over an event channel), uncaught exception handlers, errors
to exceptions handler and group of exceptions (with transactions).
[Learn more](https://central.hoa-project.net/Documentation/Library/Exception).
## Installation
With [Composer](https://getcomposer.org/), to include this library into
your dependencies, you need to
require [`hoa/exception`](https://packagist.org/packages/hoa/exception):
```sh
$ composer require hoa/exception '~1.0'
```
For more installation procedures, please read [the Source
page](https://hoa-project.net/Source.html).
## Testing
Before running the test suites, the development dependencies must be installed:
```sh
$ composer install
```
Then, to run all the test suites:
```sh
$ vendor/bin/hoa test:run
```
For more information, please read the [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html).
## Quick usage
We propose a quick overview of how to use generic exceptions, how to listen all
thrown exceptions through events and how to use group of exceptions.
### Generic exceptions
An exception is constitued of:
* A message,
* A code (optional),
* A list of arguments for the message (à la `printf`, optional),
* A previous exception (optional).
Thus, the following example builds an exception:
```php
$exception = new Hoa\Exception\Exception('Hello %s!', 0, 'world');
```
The exception message will be: `Hello world!`. The “raise” message (with all
information, not only the message) is:
```
{main}: (0) Hello world!
in … at line ….
```
Previous exceptions are shown too, for instance:
```php
$previous = new Hoa\Exception\Exception('Hello previous.');
$exception = new Hoa\Exception\Exception('Hello %s!', 0, 'world', $previous);
echo $exception->raise(true);
/**
* Will output:
* {main}: (0) Hello world!
* in … at line ….
*
* ⬇
*
* Nested exception (Hoa\Exception\Exception):
* {main}: (0) Hello previous.
* in … at line ….
*/
```
### Listen exceptions through events
Most exceptions in Hoa extend `Hoa\Exception\Exception`, which fire themselves
on the `hoa://Event/Exception` event channel (please, see [the `Hoa\Event`
library](http://central.hoa-project.net/Resource/Library/Event)). Consequently,
we can listen for all exceptions that are thrown in the application by writing:
```php
Hoa\Event\Event::getEvent('hoa://Event/Exception')->attach(
function (Hoa\Event\Bucket $bucket) {
$exception = $bucket->getData();
// …
}
);
```
Only the `Hoa\Exception\Idle` exceptions are not fired on the channel event.
### Group and transactions
Groups of exceptions are represented by the `Hoa\Exception\Group`. A group is an
exception that contains one or many exceptions. A transactional API is provided
to add more exceptions in the group with the following methods:
* `beginTransaction` to start a transaction,
* `rollbackTransaction` to remove all newly added exceptions since
`beginTransaction` call,
* `commitTransaction` to merge all newly added exceptions in the previous
transaction,
* `hasUncommittedExceptions` to check whether they are pending exceptions or
not.
For instance, if an exceptional behavior is due to several reasons, a group of
exceptions can be thrown instead of one exception. Group can be nested too,
which is useful to represent a tree of exceptions. Thus:
```php
// A group of exceptions.
$group = new Hoa\Exception\Group('Failed because of several reasons.');
$group['first'] = new Hoa\Exception\Exception('First reason');
$group['second'] = new Hoa\Exception\Exception('Second reason');
// Can nest another group.
$group['third'] = new Hoa\Exception\Group('Third reason');
$group['third']['fourth'] = new Hoa\Exception\Exception('Fourth reason');
echo $group->raise(true);
/**
* Will output:
* {main}: (0) Failed because of several reasons.
* in … at line ….
*
* Contains the following exceptions:
*
* • {main}: (0) First reason
* in … at line ….
*
* • {main}: (0) Second reason
* in … at line ….
*
* • {main}: (0) Third reason
* in … at line ….
*
* Contains the following exceptions:
*
* • {main}: (0) Fourth reason
* in … at line ….
*/
```
The following example uses a transaction to add new exceptions in the group:
```php
$group = new Hoa\Exception\Group('Failed because of several reasons.');
$group[] = new Hoa\Exception\Exception('Always present.');
$group->beginTransaction();
$group[] = new Hoa\Exception\Exception('Might be present.');
if (true === $condition) {
$group->commitTransaction();
} else {
$group->rollbackTransaction();
}
```
## Documentation
The
[hack book of `Hoa\Exception`](https://central.hoa-project.net/Documentation/Library/Exception)
contains detailed information about how to use this library and how it works.
To generate the documentation locally, execute the following commands:
```sh
$ composer require --dev hoa/devtools
$ vendor/bin/hoa devtools:documentation --open
```
More documentation can be found on the project's website:
[hoa-project.net](https://hoa-project.net/).
## Getting help
There are mainly two ways to get help:
* On the [`#hoaproject`](https://webchat.freenode.net/?channels=#hoaproject)
IRC channel,
* On the forum at [users.hoa-project.net](https://users.hoa-project.net).
## Contribution
Do you want to contribute? Thanks! A detailed [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html) explains
everything you need to know.
## License
Hoa is under the New BSD License (BSD-3-Clause). Please, see
[`LICENSE`](https://hoa-project.net/LICENSE) for details.