扩展 PHP 内置的异常处理方法

扩展 PHP 内置的异常处理类

用户可以用自定义的异常处理类来扩展 PHP 内置的异常处理类。以下的代码说明了在内置的异常处理类中，哪些属性和方法在子类中是可访问和可继承的。译者注：以下这段代码只为说明内置异常处理类的结构，它并不是一段有实际意义的可用代码。

Example #1 内置的异常处理类

class Exception

{

protected $message = 'Unknown exception'; // 异常信息protected $code = 0; // 用户自定义异常代码protected $file; // 发生异常的文件名protected $line; // 发生异常的代码行号

function __construct($message = null, $code = 0);

final function getMessage(); // 返回异常信息final function getCode(); // 返回异常代码

final function getFile(); // 返回发生异常的文件名

final function getLine(); // 返回发生异常的代码行号

final function getTrace(); // backtrace() 数组final function getTraceAsString(); // 已格成化成字符串

的 getTrace() 信息

/* 可重载的方法 */

function __toString(); // 可输出的字符串

}

?>

如果使用自定义的类来扩展内置异常处理类，并且要重新定义构造函数的话，建议同时调用parent::__construct()来检查所有的变量是否已被赋值。当对象要输出字符串的时候，可以重载__toString()并自定义输出的样式。

Example #2 扩展 PHP 内置的异常处理类

/**

* 自定义一个异常处理类

*/

class MyException extends Exception

{

// 重定义构造器使 message 变为必须被指定的属性

public function __construct($message, $code = 0) {

// 自定义的代码

// 确保所有变量都被正确赋值

parent::__construct($message, $code);

}

// 自定义字符串输出的样式

public function __toString() {

return __CLASS__ . ": [{$this->code}]: {$this->message}\n";

}

public function customFunction() {

echo "A Custom function for this type of exception\n";

}

}

/**

* 创建一个用于测试异常处理机制的类

*/

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:

// 抛出自定义异常

throw new MyException('1 is an invalid parameter', 5); // https://www.360docs.net/doc/625783932.html,

break;

case self::THROW_DEFAULT:

// 抛出默认的异常

throw new Exception('2 isnt allowed as a parameter', 6

);

break;

default:

// 没有异常的情况下，创建一个对象

$this->var = $avalue;

break;

}

}

}

// 例子 1

try {

$o = new TestException(TestException::THROW_CUSTOM);

} catch (MyException $e) { // 捕获异常

echo "Caught my exception\n", $e;

$e->customFunction();// https://www.360docs.net/doc/625783932.html,

} catch (Exception $e) { // 被忽略

echo "Caught Default Exception\n", $e;

}

// 执行后续代码

var_dump($o);

echo "\n\n";

// 例子 2

try {

$o = new TestException(TestException::THROW_DEFAULT);

} catch (MyException $e) { // 不能匹配异常的种类，被忽略echo "Caught my exception\n", $e;

$e->customFunction();

} catch (Exception $e) { // 捕获异常

echo "Caught Default Exception\n", $e;

}

// 执行后续代码

var_dump($o);

echo "\n\n";

// 例子 3

try {

$o = new TestException(TestException::THROW_CUSTOM);

} catch (Exception $e) { // 捕获异常

echo "Default Exception caught\n", $e;

}

// 执行后续代码

var_dump($o);

echo "\n\n";

// 例子 4

try {

$o = new TestException();

} catch (Exception $e) { // 没有异常，被忽略

echo "Default Exception caught\n", $e;

}

// 执行后续代码

var_dump($o);

echo "\n\n";

?>

异常处理

引用的解释

异常处理

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PHP手册

用户评论:

Dor (15-Oct-2011 10:30)

It's important to note that subclasses of the Exception class will be caught by the default Exception handler

/**

* 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) { // https://www.360docs.net/doc/625783932.html,

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).

joechrz at gmail dot com (18-Feb-2010 11:18)

It's important to note some unexpected behavior when overriding the

__toString method of an Exception. https://www.360docs.net/doc/625783932.html, The default PHP exception handler will truncate the result of the __toString method to the number of bytes specified by log_errors_max_len in php.ini.

To get around this problem, you need to either change the value of

log_errors_max_len:

// recommended: disable error logging

// so the log files don't become bloated from huge

// exception strings

ini_set('log_errors','off');

// log_errors_max_len = infinite length

ini_set("log_errors_max_len",0);

?>

or specify a custom exception handler:

function long_exception_handler($exception) {

// for compatibility, call __toString

echo $exception->__toString();

}

set_exception_handler('long_exception_handler');

?>

iamhiddensomewhere at gmail dot com (31-Dec-2009 11:17)

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:

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.

https://www.360docs.net/doc/625783932.html, (24-Nov-2009 03:37)

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.

paragdiwan at gmail dot com (17-Jan-2009 09:32)

I have written similar simple custom exception class. Helpful for newbie.

/*

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);

} // https://www.360docs.net/doc/625783932.html,

public function __toString()

{

return "".$this->message."";

}

}

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;

}

?>