Check the other SPL Exception classes and extend one of those if your intended exception is a subclass of one of those. This allows more finesse when catching.
Exceptions erweitern
Eine benutzerdefinierte Exceptionklasse kann durch Ableitung von der eingebauten Exceptionklasse erstellt werden. Die unten angegebenen Methoden und Eigenschaften zeigen, was innerhalb der Kindklasse von der eingebauten Exceptionklasse verfügbar ist.
Beispiel #1 Die eingebaute Exceptionklasse
<?php
class Exception implements Throwable
{
protected $message = 'Unknown exception'; // Exceptionmitteilung
private $string; // __toString-Cache
protected $code = 0; // Benutzerdefinierte Fehlernummer
protected $file; // Quelldateiname der Exception
protected $line; // Quelldateizeile der Exception
private $trace; // Rückverfolgung
private $previous; // Vorherige Exception, falls verschachtelte Exception
public function __construct($message = '', $code = 0, Throwable $previous = null);
final private function __clone(); // Verhindert klonen von Exceptions
final public function getMessage(); // Mitteilung der Exception
final public function getCode(); // Fehlercode der Exception
final public function getFile(); // Quelldateiname
final public function getLine(); // Quelldateizeile
final public function getTrace(); // Array zum Rückverfolgen
final public function getPrevious(); // Vorherige Exception
final public function getTraceAsString(); // Formatierter String der Rückverfolgung
// Überschreibbar
public function __toString(); // Formatierter String für die Ausgabe
}
?>Wenn eine Klasse die eingebaute Exceptionklasse erweitert und den Konstruktor neu definiert, ist es dringend empfohlen, dass der Konstruktor der Klasse parent::__construct() aufruft, um sicherzustellen, dass alle verfügbaren Daten korrekt zugewiesen wurden. Die __toString()-Methode kann überschrieben werden, um eine benutzerdefinierte Ausgabe anzubieten, wenn das Objekt durch eine Zeichenkette repräsentiert werden soll.
Hinweis:
Exceptions können nicht geklont werden. Der Versuch, eine Exception zu klonen, wird einen fatalen
E_ERROR-Fehler zur Folge haben.
Beispiel #2 Die Exceptionklasse erweitern
<?php
/**
* Eine eigene Exceptionklasse definieren
*/
class MyException extends Exception
{
// Die Exception neu definieren, damit die Mitteilung nicht optional ist
public function __construct($message, $code = 0, Throwable $previous = null) {
// etwas Code
// sicherstellen, dass alles korrekt zugewiesen wird
parent::__construct($message, $code, $previous);
}
// benutzerdefinierte Stringdarstellung des Objektes
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "Eine eigene Funktion für diesen Exceptiontyp\n";
}
}
/**
* Erzeuge eine Klasse, um die Exception zu testen
*/
class TestException
{
public $var;
const THROW_NONE = 0;
const THROW_CUSTOM = 1;
const THROW_DEFAULT = 2;
function __construct($avalue = self::THROW_NONE) {
switch ($avalue) {
case self::THROW_CUSTOM:
// eigene Exception auslösen
throw new MyException('1 ist ein ungültiger Parameter', 5);
break;
case self::THROW_DEFAULT:
// Vorgabe werfen
throw new Exception('2 ist kein zugelassener Parameter', 6);
break;
default:
// Keine Exception; das Objekt wird erzeugt
$this->var = $avalue;
break;
}
}
}
// Beispiel 1
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (MyException $e) { // Wird gefangen
echo "Meine Exception gefangen\n", $e;
$e->customFunction();
} catch (Exception $e) { // Übersprungen
echo "Standardexception gefangen\n", $e;
}
// Ausführung fortsetzen
var_dump($o); // Null
echo "\n\n";
// Beispiel 2
try {
$o = new TestException(TestException::THROW_DEFAULT);
} catch (MyException $e) { // Dieser Typ passt nicht
echo "Meine Exception gefangen\n", $e;
$e->customFunction();
} catch (Exception $e) { // Wird gefangen
echo "Standardexception gefangen\n", $e;
}
// Ausführung fortsetzen
var_dump($o); // Null
echo "\n\n";
// Beispiel 3
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (Exception $e) { // Wird gefangen
echo "Standardexception gefangen\n", $e;
}
// Ausführung fortsetzen
var_dump($o); // Null
echo "\n\n";
// Beispiel 4
try {
$o = new TestException();
} catch (Exception $e) { // Übersprungen, keine Exception ausgelöst
echo "Standardexception gefangen\n", $e;
}
// Ausführung fortsetzen
var_dump($o); // TestException
echo "\n\n";
?>
add a note
User Contributed Notes 8 notes
Hayley Watson ¶
5 years ago
iamhiddensomewhere at gmail dot com ¶
14 years ago
As previously noted exception linking was recently added (and what a god-send it is, it certainly makes layer abstraction (and, by association, exception tracking) easier).
Since <5.3 was lacking this useful feature I took some initiative and creating a custom exception class that all of my exceptions inherit from:
<?php
class SystemException extends Exception
{
private $previous;
public function __construct($message, $code = 0, Exception $previous = null)
{
parent::__construct($message, $code);
if (!is_null($previous))
{
$this -> previous = $previous;
}
}
public function getPrevious()
{
return $this -> previous;
}
}
?>
Hope you find it useful.
sapphirepaw.org ¶
14 years ago
Support for exception linking was added in PHP 5.3.0. The getPrevious() method and the $previous argument to the constructor are not available on any built-in exceptions in older versions of PHP.
michaelrfairhurst at gmail dot com ¶
12 years ago
Custom exception classes can allow you to write tests that prove your exceptions
are meaningful. Usually testing exceptions, you either assert the message equals
something in which case you can't change the message format without refactoring,
or not make any assertions at all in which case you can get misleading messages
later down the line. Especially if your $e->getMessage is something complicated
like a var_dump'ed context array.
The solution is to abstract the error information from the Exception class into
properties that can be tested everywhere except the one test for your formatting.
<?php
class TestableException extends Exception {
private $property;
function __construct($property) {
$this->property = $property;
parent::__construct($this->format($property));
}
function format($property) {
return "I have formatted: " . $property . "!!";
}
function getProperty() {
return $this->property;
}
}
function testSomethingThrowsTestableException() {
try {
throw new TestableException('Property');
} Catch (TestableException $e) {
$this->assertEquals('Property', $e->getProperty());
}
}
function testExceptionFormattingOnlyOnce() {
$e = new TestableException;
$this->assertEquals('I have formatted: properly for the only required test!!',
$e->format('properly for the only required test')
);
}
?>
Dor ¶
13 years ago
It's important to note that subclasses of the Exception class will be caught by the default Exception handler
<?php
/**
* NewException
* Extends the Exception class so that the $message parameter is now mendatory.
*
*/
class NewException extends Exception {
//$message is now not optional, just for the extension.
public function __construct($message, $code = 0, Exception $previous = null) {
parent::__construct($message, $code, $previous);
}
}
/**
* TestException
* Tests and throws Exceptions.
*/
class TestException {
const NONE = 0;
const NORMAL = 1;
const CUSTOM = 2;
public function __construct($type = self::NONE) {
switch ($type) {
case 1:
throw new Exception('Normal Exception');
break;
case 2:
throw new NewException('Custom Exception');
break;
default:
return 0; //No exception is thrown.
}
}
}
try {
$t = new TestException(TestException::CUSTOM);
}
catch (Exception $e) {
print_r($e); //Exception Caught
}
?>
Note that if an Exception is caught once, it won't be caught again (even for a more specific handler).
shaman_master at list dot ru ¶
9 years ago
Use this example for not numeric codes:
<code>
<?php
class MyException extends Exception
{
/**
* Creates a new exception.
*
* @param string $message Error message
* @param mixed $code The exception code
* @param Exception $previous Previous exception
* @return void
*/
public function __construct($message = '', $code = 0, Exception $previous = null)
{
// Pass the message and integer code to the parent
parent::__construct((string)$message, (int)$code, $previous);
// @link http://bugs.php.net/39615 Save the unmodified code
$this->code = $code;
}
}
</code>
florenxe ¶
9 years ago
I just wanted to add that "extends" is same concept of "Inheritance" or "Prototyping in Javascript". So when you extend a class, you are simply inheriting the class's methods and properties. So you can create custom classes from existing classes like extending the array class.
paragdiwan at gmail dot com ¶
15 years ago
I have written similar simple custom exception class. Helpful for newbie.
<?php
/*
This is written for overriding the exceptions.
custom exception class
*/
error_reporting(E_ALL-E_NOTICE);
class myCustomException extends Exception
{
public function __construct($message, $code=0)
{
parent::__construct($message,$code);
}
public function __toString()
{
return "<b style='color:red'>".$this->message."</b>";
}
}
class testException
{
public function __construct($x)
{
$this->x=$x;
}
function see()
{
if($this->x==9 )
{
throw new myCustomException("i didnt like it");
}
}
}
$obj = new testException(9);
try{
$obj->see();
}
catch(myCustomException $e)
{
echo $e;
}
?>
