PHP handles exceptions. Exception is the eponymous class, that is the mother of most of the exceptions : PHP's SPL exceptions, extensions Exceptions (mysqli, pdo, phar, soap, etc..) and, eventually, the one in the final application.
PHP 7 introduces a new Exception, called BaseException. This will take over the position of 'mother of all exceptions'. This means that code relying on Exception may now let the new EngineException and ParseException pass and generate a fatal error.
Thrown exceptions should inherit from Exception. This way, they may be selectively caught by a try...catch structure.
<?php
try {
/* Some Code */
throw new MyException('Message');
} catch (MyException $e) {
// Catch all
}
?>Exceptions may be grouped for catch with an extra level of inheritance :
<?php
class WeekException extends Exception {}
class MonthException extends Exception {}
class MondayException extends WeekException {}
class TuesdayException extends WeekException {}
/*...*/
class JanuaryException extends MonthException {}
/*...*/
try {
/* on Monday */
throw new MondayException('Message');
/* on Tuesday */
throw new TuesdayException('Message');
} catch (WeekException $e) {
// Process weekdays exceptions
// do not process month exceptions
}
?>Exceptions may also be nested : by throwing a new exception that include the previous one, both messages will be carried to the next try...catch.
<?php
try {
/* on Monday */
throw new MondayException('Message');
} catch (WeekException $e) {
// Process monday exceptions
throw new JanuaryException('Week day exception caught in January', null, $e);
}
?>Last, there are already 13 exceptions predefined in SPL extension :
- BadFunctionCallException
- BadMethodCallException
- DomainException
- InvalidArgumentException
- LengthException
- LogicException
- OutOfBoundsException
- OutOfRangeException
- OverflowException
- RangeException
- RuntimeException
- UnderflowException
- UnexpectedValueException
They provide some general semantics for Exceptions and may be used to help libraries understand each other's exception.
As Exception should be specialized, catching a precise type of exception should be preferred over catching Exception : this last one is actually reserved for a catch-all feature.
It is recommended to extends the Exception and never directly use this class.
The following code is considered a warning:
<?php
namespace X;
try {
/* Some Code */
throw new Exception('Message');
} catch (Exception $e) {
// Catch all for the namespace if such class exists
} catch (\Exception $e) {
// Catch all
}
?>The following pattern is considered legit:
<?php
try {
/* Some Code */
throw new MyException('Message');
} catch (DomainException $e) {
// Catch SPL-inheriting exception
} catch (MySpecialException $e) {
// Catch only my special type of exception
}
class MyException extends \DomainException {}
class MySpecialException extends \Exception {}
?>- PHP Exceptions
- SPL Exceptions
- [Exception Best Practices in PHP 5.3] (http://ralphschindler.com/2010/09/15/exception-best-practices-in-php-5-3)
- PHP 7 Exceptions