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.
例外を拡張する
組み込みの Exception クラスを拡張することで、例外クラスをユーザーが 定義することが可能です。以下のメンバーおよびプロパティは、 組み込みの Exception クラスから派生した子クラスの中でアクセス可能です。
例1 組み込みの例外クラス
<?php
class Exception implements Throwable
{
protected $message = 'Unknown exception'; // exception message
private $string; // __toString cache
protected $code = 0; // user defined exception code
protected $file; // source filename of exception
protected $line; // source line of exception
private $trace; // backtrace
private $previous; // previous exception if nested exception
public function __construct($message = '', $code = 0, Throwable $previous = null);
final private function __clone(); // Inhibits cloning of exceptions.
final public function getMessage(); // message of exception
final public function getCode(); // code of exception
final public function getFile(); // source filename
final public function getLine(); // source line
final public function getTrace(); // an array of the backtrace()
final public function getPrevious(); // previous exception
final public function getTraceAsString(); // formatted string of trace
// Overrideable
public function __toString(); // formatted string for display
}
?>クラスが、組み込みの Exception クラスを拡張し、 コンストラクタを再定義した場合、 全ての利用可能なデータが正しく代入されることを保証するために parent::__construct() もコールすることが強く推奨されます。 __toString() メソッドは、 オブジェクトが文字列として表された際に独自の出力を行うために 上書きすることができます。
注意:
例外を複製することはできません。Exception を clone しようとすると 致命的な
E_ERRORエラーが発生します。
例2 例外クラスを拡張する
<?php
/**
* カスタム例外クラスを定義する
*/
class MyException extends Exception
{
// 例外を再定義し、メッセージをオプションではなくする
public function __construct($message, $code = 0, Throwable $previous = null) {
// なんらかのコード
// 全てを正しく確実に代入する
parent::__construct($message, $code, $previous);
}
// オブジェクトの文字列表現を独自に定義する
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "A custom function for this type of exception\n";
}
}
/**
* 例外をテストするためのクラスを作成
*/
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:
// カスタム例外をスローする
throw new MyException('1 is an invalid parameter', 5);
break;
case self::THROW_DEFAULT:
// デフォルトの例外をスローする
throw new Exception('2 is not allowed as a parameter', 6);
break;
default:
// 例外が発生しなかった。オブジェクトが生成される
$this->var = $avalue;
break;
}
}
}
// 例1
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (MyException $e) { // ここでキャッチされる
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // ここはスキップされる
echo "Caught Default Exception\n", $e;
}
// 実行を継続する
var_dump($o); // Null
echo "\n\n";
// 例2
try {
$o = new TestException(TestException::THROW_DEFAULT);
} catch (MyException $e) { // この型にはマッチしない
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // ここでキャッチされる
echo "Caught Default Exception\n", $e;
}
// 実行を継続する
var_dump($o); // Null
echo "\n\n";
// 例3
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (Exception $e) { // ここでキャッチされる
echo "Default Exception caught\n", $e;
}
// 実行を継続する
var_dump($o); // Null
echo "\n\n";
// 例4
try {
$o = new TestException();
} catch (Exception $e) { // スキップされる、例外は発生しない
echo "Default Exception caught\n", $e;
}
// 実行を継続する
var_dump($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 ¶
15 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 ¶
10 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;
}
?>
