Catcher uses classes called _handlers_ to handle throwables sent its way. PHP is currently in a state of flux when it comes to errors. There are traditional PHP errors which are triggered in userland by using `trigger_error()` which can't be caught using `try`/`catch` and are generally a pain to work with. PHP has begun to remedy this problem by introducing the `\Error` class and its various child classes. However, a lot of functions and core aspects of the language itself continue to use legacy errors. This class does away with this pain point in PHP by turning all errors into throwables. When Catcher converts legacy errors into throwables it will only exit if PHP would, so warnings, notices, etc. won't cause the program to exit unless you configure it to do so. Non user-level fatal errors are picked up by Catcher using its shutdown handler. This means that simply by invoking Catcher one may now... catch (almost) any error PHP then handles.
For most use cases this library requires no configuration and little effort to integrate into non-complex environments:
```php
use MensBeam\Foundation\Catcher;
$catcher = new Catcher();
```
That's it. It will automatically register Catcher as an exception, error, and shutdown handler and use `PlainTextHandler` as its sole handler. Catcher can be configured to use one or multiple _handlers_. Imagine a situation where it is necessary to both output text for logging and JSON for an API endpoint. This is easily done using Catcher:
```php
use MensBeam\Foundation\Catcher,
Monolog\Logger;
use MensBeam\Foundation\Catcher\{
JSONHandler,
PlainTextHandler
};
$catcher = new Catcher(
new PlainTextHandler([
'logger' => new Logger('log'),
'silent' => true
]),
new JSONHandler()
);
```
The example above uses [Monolog][b] for its logger, but any PSR-3-compatible logger will work. The `PlainTextHandler` is configured to use a logger where then it will send any and all errors to the logger to do with as it pleases. It is also configured to be otherwise silent. `JSONHandler` is then configured using its default configuration. Handlers are placed within a stack and executed in the order by which they are fed to Catcher, so in this case `PlainTextHandler` will go first, logging the error. `JSONHandler` will follow afterwards and print the JSON.
Catcher comes built-in with the following handlers:
*`HTMLHandler` – Outputs errors in a clean HTML document; uses DOM to assemble the document.
*`JSONHandler` – Outputs errors in a JSON format mostly representative of how errors are stored internally by Catcher handlers; it is provided as an example. The decision to make it like this was made because errors often need to be represented according to particular requirements or even a specification, and we cannot possibly support them all. `JSONHandler`, however, can be easily extended to suit individual project needs.
*`PlainTextHandler` – Outputs errors cleanly in plain text meant mostly for command line use and also provides for logging
This is the main class in the library. Unless you have a need to configure a handler or use multiple handlers there usually isn't a need to interact with the rest of the library at all.
Returns the last throwable that this instance of Catcher has handled
#### MensBeam\Foundation\Catcher::isRegistered
Returns whether the Catcher still is registered as a error, exception, and shutdown handler
#### MensBeam\Foundation\Catcher::popHandler
Pops the last handler off the stack and returns it
#### MensBeam\Foundation\Catcher::pushHandler
Pushes the specified handler(s) onto the stack
#### MensBeam\Foundation\Catcher::register
Registers the Catcher instance as an error, exception, and shutdown handler. By default the constructor does this automatically, but this method exists in case `unregister` has been called.
#### MensBeam\Foundation\Catcher::setHandlers
Replaces the stack of handlers with those specified as parameters.
All handlers inherit from this abstract class. Since it is an abstract class meant for constructing handlers protected methods and properties will be documented here as well.
_CONTENT\_TYPE_: The mime type of the content that is output by the handler
_CONTINUE_: When returned within the control code bitmask in the handler's output array, it causes the stack loop to continue onto the next handler after handling; this is the default behavior.
_BREAK_: When returned within the control code bitmask in the handler's output array, it causes the stack loop to break after the handler finishes, causing any further down in the stack to not run.
_EXIT_: When returned within the control code bitmask in the handler's output array, it causes Catcher to exit after running all handlers.
_OUTPUT_: When returned within the output code bitmask in the handler's output array, it causes the handler to output the throwable when dispatching.
_SILENT_: When returned within the output code bitmask in the handler's output array, it causes the handler to be silent.
_NOW_: When returned within the output code bitmask in the handler's output array, it causes Catcher to have the handler immediately dispatch.
_outputBuffer_: This is where the output arrays representing the handled throwables are stored until they are dispatched.
#### Options
Properties which begin with an underscore all are options. They can be set either through the constructor or via `setHandler` by name, removing the underscore at the beginning. All handlers inherit these options. Options in inherited classes should also begin with an underscore (_\__). How to extend `Handler` will be explained further down in the document.
_backtraceArgFrameLimit_: The number of frames by which there can be arguments output with them. Defaults to _5_.
_charset_: The character set of the output; only used if headers weren't sent before an error occurred. No conversion is done. Defaults to _"UTF\_8"_.
_forceBreak_: When set this will force the stack loop to break after the handler has run. Defaults to _false_.
_forceExit_: When set this will force an exit after all handlers have been run. Defaults to _false_.
_forceOutputNow_: When set this will force output of the handler immediately. Defaults to _false_.
_httpCode_: The HTTP code to be sent; possible values are 200, 400-599. Defaults to _500_.
_outputBacktrace_: When true will output a stack trace. Defaults to _false_.
_outputPrevious_: When true will output previous throwables. Defaults to _true_.
_outputTime_: When true will output times to the output. Defaults to _true_.
_outputToStderr_: When the SAPI is cli output errors to stderr. Defaults to _true_.
_silent_: When true the handler won't output anything. Defaults to _false_.
_timeFormat_: The PHP-standard date format which to use for times in output. Defaults to _"Y-m-d\\TH:i:s.vO"_.
"Cleans" an output throwable -- an individual item in the output array -- by removing information that's unnecessary in the output; useful for structured data output such as JSON.
We cannot require all throwables to be converted to our own classes, so this class exists as a controller to add new features to throwables for use with Catcher.
Returns the error type of a `MensBeam\Foundation\Catcher\Error`, meaning a human-friendly representation of the error code (eg: _"Fatal Error"_, _"Warning"_, _"Notice"_) or null if the throwable isn't an `Error`.
The default handlers, especially `PlainTextHandler`, are set up to handle most tasks, but obviously more is possible with a bit of work. Thankfully, creating handlers is as simple as extending the `Handler` class. Here is an example of a theoretical `YamlHandler` (which is very similar to `JSONHandler`):
This theoretical class uses the [`symfony/yaml`][c] package in Composer and exposes a few of its options as options for the Handler. Using this class would be very similar to the examples provided at the beginning of this document:
```php
use Mensbeam\Foundation\Catcher,
Your\Namespace\Goes\Here\YamlHandler;
$catcher = new Catcher(new YamlHandler([
'outputNullAsTilde' => true
]);
```
More complex handlers are possible by extending the various methods documented above. Examples can be seen by looking at the code for both `HTMLHandler` and `PlainTextHandler`.
