php异常处理

php异常处理Table of Contents扩展（extend）PHP 内置的异常处理类PHP 5 has an exception model similar to that of other programming languages. An exception can be thrown, and caught ("catched") within PHP. Code may be surrounded in a try block, to facilitate the catching of potential exceptions. Each try must have at least one corresponding catch or finally block.The thrown object must be an instance of the Exception class or a subclass of Exception. Trying to throw an object that is not will result in a PHP Fatal Error.catchMultiple catch blocks can be used to catch different classes of exceptions. Normal execution (when no exception is thrown within the try block) will continue after that last catch block defined in sequence. Exceptions can be thrown (or re-thrown) within a catch block.When an exception is thrown, code following the statement will not be executed, and PHP will attempt to find the first matching catch block. If an exception is not caught, a PHP Fatal Error will be issued with an "Uncaught Exception ..." message, unless a handler has been defined with set_exception_handler().finallyIn PHP 5.5 and later, a finally block may also be specified after or instead of catch blocks. Code within the finally block will always be executed after the try and catch blocks, regardless of whether an exception has been thrown, and before normal execution resumes.注释Note:Internal PHP functions mainly use Error reporting, only modern Object oriented extensions use exceptions. However, errors can be simply translated to exceptions with ErrorException.TipThe Standard PHP Library (SPL) provides a good number of built-in exceptions.范例Example #3 Throwing an Exception<?phpfunction inverse($x) {if (!$x) {throw new Exception('Division by zero.');}return 1/$x;}try {echo inverse(5) . "\n";echo inverse(0) . "\n";} catch (Exception $e) {echo 'Caught exception: ', $e->getMessage(), "\n"; }// Continue executionecho "Hello World\n";?>以上例程会输出：0.2Caught exception: Division by zero.Hello WorldExample #4 Exception handling with a finally block<?phpfunction inverse($x) {if (!$x) {throw new Exception('Division by zero.');}return 1/$x;}try {echo inverse(5) . "\n";} catch (Exception $e) {echo 'Caught exception: ', $e->getMessage(), "\n"; } finally {echo "First finally.\n";}try {echo inverse(0) . "\n";} catch (Exception $e) {echo 'Caught exception: ', $e->getMessage(), "\n"; } finally {echo "Second finally.\n";}// Continue executionecho "Hello World\n";?>以上例程会输出：0.2First finally.Caught exception: Division by zero.Second finally.Hello WorldExample #5 Nested Exception<?phpclass MyException extends Exception { }class Test {public function testing() {try {try {throw new MyException('foo!');} catch (MyException $e) {// rethrow itthrow $e;}} catch (Exception $e) {var_dump($e->getMessage());}}}$foo = new Test;$foo->testing();?>以上例程会输出：string(4) "foo!"add a note add a noteUser Contributed Notes 26 notesupdown135 zmunoz at gmail dot com ¶6 years agoWhen catching an exception inside a namespace it is important that you escape to the global space:<?phpnamespace SomeNamespace;class SomeClass {function SomeFunction() {try {throw new Exception('Some Error Message');} catch (\Exception $e) {var_dump($e->getMessage());}}}?>updown72 Johan ¶5 years agoCustom error handling on entire pages can avoid half rendered pages for the users:<?phpob_start();try {/*contains all page logicand throws error if needed*/...} catch (Exception $e) {ob_end_clean();displayErrorPage($e->getMessage());}?>updown9 ohcc at 163 dot com ¶9 months agoType declarations will trigger Uncaught TypeError when a different type is passed. And it cannot be caught with the Exception class.<?phpfunction xc(array $a){}try{xc(4);}catch (Exception $e){ // failed to catch itecho $e->getMessage();}?>You should use TypeError instead for PHP 7+,<?phpfunction xc(array $a){}try{xc(4);}catch (TypeError $e){echo $e->getMessage();}?>In php version prior to 7.0, you should translate Catchable fatal errors to an exception and then catch it.<?phpfunction exceptionErrorHandler($errNumber, $errStr, $errFile, $errLine ) {throw new ErrorException($errStr, 0, $errNumber, $errFile, $errLine);}set_error_handler('exceptionErrorHandler');function s(array $a){}try{s(4);}catch (Exception $e){echo $e->getMessage();}?>updown49 ask at nilpo dot com ¶7 years agoIf you intend on creating a lot of custom exceptions, you may find this code useful. I've created an interface and an abstract exception class that ensures that all parts of the built-in Exception class are preserved in child classes. It also properly pushes all information back to the parent constructor ensuring that nothing is lost. This allows you to quickly create new exceptions on the fly. It also overrides the default __toString method with a more thorough one.<?phpinterface IException{/* Protected methods inherited from Exception class */public function getMessage(); // Exception messagepublic function getCode(); // User-defined Exception code public function getFile(); // Source filenamepublic function getLine(); // Source linepublic function getTrace(); // An array of the backtrace()public function getTraceAsString(); // Formated string of trace/* Overrideable methods inherited from Exception class */public function __toString(); // formated string for displaypublic function __construct($message = null, $code = 0);}abstract class CustomException extends Exception implements IException{protected $message = 'Unknown exception'; // Exception messageprivate $string; // Unknownprotected $code = 0; // User-defined exception code protected $file; // Source filename of exception protected $line; // Source line of exceptionprivate $trace; // Unknownpublic function __construct($message = null, $code = 0){if (!$message) {throw new $this('Unknown '. get_class($this));}parent::__construct($message, $code);}public function __toString(){return get_class($this) . " '{$this->message}' in {$this->file}({$this->line})\n". "{$this->getTraceAsString()}";}}?>Now you can create new exceptions in one line:<?phpclass TestException extends CustomException {}?>Here's a test that shows that all information is properly preserved throughout the backtrace.<?phpfunction exceptionTest(){try {throw new TestException();}catch (TestException $e) {echo "Caught TestException ('{$e->getMessage()}')\n{$e}\n";}catch (Exception $e) {echo "Caught Exception ('{$e->getMessage()}')\n{$e}\n";}}echo '<pre>' . exceptionTest() . '</pre>';?>Here's a sample output:Caught TestException ('Unknown TestException')TestException 'Unknown TestException' in C:\xampp\htdocs\CustomException\CustomException.php(31)#0 C:\xampp\htdocs\CustomException\ExceptionTest.php(19): CustomException->__construct() #1 C:\xampp\htdocs\CustomException\ExceptionTest.php(43): exceptionTest()#2 {main}updown7 hweidmann at online dot de ¶11 months agocatch doesn't check for the existence of the Exception class, so avoid typo.<?phpclass MyException extends Exception{...}try{throw new MyException(...);}catch (MuException $e) // <--- typo{...}?>You WON'T getFatal error: Class MuException could not be loaded ...You WILL getFatal error: Uncaught exception 'MyException' ...updown23 php at marcuspope dot com ¶2 years agoUsing a return statement inside a finally block will override any other return statement or thrown exception from the try block and all defined catch blocks. Code execution in the parent stack will continue as if the exception was never thrown.Frankly this is a good design decision because it means I can optionally dismiss all thrown exceptions from 1 or more catch blocks in one place, without having to nest my whole try block inside an additional (and otherwise needless) try/catch block.This is the same behavior as Java, whereas C# throws a compile time error when a return statement exists inside a finally block. So I figured it was worth pointing out to PHP devs who may not have any exposure to finally blocks or how other languages do it.<?phpfunction asdf(){try {throw new Exception('error');}catch(Exception $e) {echo "An error occurred";throw $e;}finally {//This overrides the exception as if it were never thrownreturn "\nException erased";}}try {echo asdf();}catch(Exception $e) {echo "\nResult: " . $e->getMessage();}?>The output from above will look like this:An error occurredException erasedWithout the return statement in the finally block it would look like this:An error occurredResult: errorupdown16 jazfresh at ¶10 years agoSometimes you want a single catch() to catch multiple types of Exception. In a language like Python, you can specify multiple types in a catch(), but in PHP you can only specify one. This can be annoying when you want handle many different Exceptions with the same catch() block.However, you can replicate the functionality somewhat, because catch(<classname> $var) will match the given <classname> *or any of it's sub-classes*.For example:<?phpclass DisplayException extends Exception {};class FileException extends Exception {};class AccessControl extends FileException {}; // Sub-class of FileExceptionclass IOError extends FileException {}; // Sub-class of FileExceptiontry {if(!is_readable($somefile))throw new IOError("File is not readable!");if(!user_has_access_to_file($someuser, $somefile))throw new AccessControl("Permission denied!");if(!display_file ($somefile))throw new DisplayException("Couldn't display file!");} catch (FileException $e) {// This block will catch FileException, AccessControl or IOError exceptions, but not Exceptionsor DisplayExceptions.echo "File error: ".$e->getMessage();exit(1);}?>Corollary: If you want to catch *any* exception, no matter what the type, just use "catch(Exception $var)", because all exceptions are sub-classes of the built-in Exception.updown10 jim at anderos dot com ¶2 years agoIf you are using a namespace, you must indicate the global namespace when using Exceptions. <?phpnamespace alpha;function foo(){throw new \Exception("Something is wrong!");// throw new Exception(""); will fail}try {foo();} catch( \Exception $e ) {// catch( Exception $e ) will give no warning, but will not catch Exceptionecho "ERROR: $e";}?>updown12 Edu ¶3 years agoThe "finally" block can change the exception that has been throw by the catch block.<?phptry{try {throw new \Exception("Hello");} catch(\Exception $e) {echo $e->getMessage()." catch in\n";throw $e;} finally {echo $e->getMessage()." finally \n";throw new \Exception("Bye");}} catch (\Exception $e) {echo $e->getMessage()." catch out\n";}?>The output is:Hello catch inHello finallyBye catch outupdown12 sander at rotorsolutions dot nl ¶3 years agoJust an example why finally blocks are usefull (5.5)<?php//without catchfunction example() {try {//do something that throws an exeption}finally {//this code will be executed even when the exception is executed}}function example2() {try {//open sql connection check user as exampleif(condition) {return false;}}finally {//close the sql connection, this will be executed even if the return is called.}}?>updown8 Shot (Piotr Szotkowski) ¶7 years ago‘Normal execution (when no exception is thrown within the try block, *or when a catch matching the thrown exception’s class is not present*) will continue after that last catch blockdefined in sequence.’‘If an exception is not caught, a PHP Fatal Error will be issued with an “Uncaught Exception …”message, unless a handler has been defined with set_exception_handler().’These two sentences seem a bit contradicting about what happens ‘when a catch matching the thrown exception’s class is not present’(and the second sentence is actually correct).updown5 telefoontoestel at nospam dot org ¶2 years agoWhen using finally keep in mind that when a exit/die statement is used in the catch block it will NOT go through the finally block.<?phptry {echo "try block<br />";throw new Exception("test");} catch (Exception $ex) {echo "catch block<br />";} finally {echo "finally block<br />";}// try block// catch block// finally block?><?phptry {echo "try block<br />";throw new Exception("test");} catch (Exception $ex) {echo "catch block<br />";exit(1);} finally {echo "finally block<br />";}// try block// catch block?>updown1 Mohammad Hossein Darvishanpour ¶4 months ago<?phpfunction Test_Extention($var1){if($var1 == false){throw new Exception('Invalid !');}}//end functiontry{Test_Extention(false);printf("%s","Valid");}catch(Exception $e){printf("%s","Message : " . $e->getMessage());}?>updown4 Simo ¶1 year ago#3 is not a good example. inverse("0a") would not be caught since (bool) "0a" returns true, yet 1/"0a" casts the string to integer zero and attempts to perform the calculation.updown12 michael dot ochs at gmx dot net ¶8 years agoActually it isn't possible to do:<?phpsomeFunction() OR throw new Exception();?>This leads to a T_THROW Syntax Error. If you want to use this kind of exceptions, you can do the following:<?phpfunction throwException($message = null,$code = null) {throw new Exception($message,$code);}someFunction() OR throwException();?>updown5 cyrus+php at boadway dot ca ¶2 years agoThere's some inconsistent behaviour associated with PHP 5.5.3's finally and return statements. If a method returns a variable in a try block (e.g. return $foo;), and finally modifies that variable, the /modified/ value is returned. However, if the try block has a return that has to be evaluated in-line (e.g. return $foo+0;), finally's changes to $foo will /not/ affect the return value.[code]function returnVariable(){$foo = 1;try{return $foo;} finally {$foo++;}}function returnVariablePlusZero(){$foo = 1;try{return $foo + 0;} finally {$foo++;}}$test1 = returnVariable(); // returns 2, not the correct value of 1.$test2 = returnVariablePlusZero(); // returns correct value of 1, but inconsistent with $test1.[/code]It looks like it's trying to be efficient by not allocating additional memory for the return value when it thinks it doesn't have to, but the spec is that finally is run after try is completed execution, and that includes the evaluation of the return expression.One could argue (weakly) that the first method should be the correct result, but at least the two methods should be consistent.updown3 sander at rotorsolutions dot nl ¶3 years agoJust an example why finally blocks are usefull (5.5)<?php//without catchfunction example() {try {//do something that throws an exeption}finally {//this code will be executed even when the exception is executed}}function example2() {try {//open sql connection check user as exampleif(condition) {return false;}}finally {//close the sql connection, this will be executed even if the return is called.}}updown1 ohcc at 163 dot com ¶19 days agoIf a TRY has a FINALLY, a RETURN either in the TRY or a CATCH won't terminate the script. Code in the same block after the RETURN will not be executed, and the RETURN itself will be "copied" to the bottom of the FINALLY block to be executed.a RETURN in the FINALLY block will override value(s) returned from the TRY or a CATCH block.An EXIT or a DIE always terminate the script after themselves.code 1<?phpfunction foo(){$bar = 1;try{throw new Exception('I am Wu Xiancheng.');}catch(Exception $e){return $bar;$bar--; // this line will be ignored}finally{$bar++;}}echo foo(); // 2?>code 2<?phpfunction foo(){$bar = 1;try{throw new Exception('I am Wu Xiancheng.');}catch(Exception $e){return $bar;$bar--; // this line will be ignored}finally{$bar++;return $bar;}}echo foo(); //2?>code 3<?phpfunction foo(){$bar = 1;try{throw new Exception('I am Wu Xiancheng.');}catch(Exception $e){return $bar;$bar--; // this line will be ignored}finally{return 100;}}echo foo(); //100?>updown1 fjoggen at gmail dot com ¶10 years agoThis code will turn php errors into exceptions:<?phpfunction exceptions_error_handler($severity, $message, $filename, $lineno) {throw new ErrorException($message, 0, $severity, $filename, $lineno);}set_error_handler('exceptions_error_handler');?>However since <?php set_error_handler()?> doesn't work with fatal errors, you will not be able to throw them as Exceptions.updown0 omnibus at omnibus dot edu dot pl ¶8 years agoJust to be more precise in what Frank found:Catch the exceptions always in order from the bottom to the top of the Exception and subclasses class hierarchy. If you have class MyException extending Exception and class My2Exception extending MyException always catch My2Exception before MyException.Hope this helpsupdown0 jon at hackcraft dot net ¶9 years agoFurther to dexen at google dot me dot up with "use destructors to perform a cleanup in case of exception". The fact that PHP5 has destructors, exception handling, and predictable garbage collection (if there's a single reference in scope and the scope is left then the destructor is called immediately) allows for the use of the RAII idiom./wiki/Resource_Acquisition_Is_Initialization and my own /RAII/ describe this.updown-1 Sawsan ¶4 years agothe following is an example of a re-thrown exception and the using of getPrevious function:<?php$name = "Name";//check if the name contains only letters, and does not contain the word nametry{try{if (preg_match('/[^a-z]/i', $name)){throw new Exception("$name contains character other than a-z A-Z");}if(strpos(strtolower($name), 'name') !== FALSE){throw new Exception("$name contains the word name");}echo "The Name is valid";}catch(Exception $e){throw new Exception("insert name again",0,$e);}}catch (Exception $e){if ($e->getPrevious()){echo "The Previous Exception is: ".$e->getPrevious()->getMessage()."<br/>";}echo "The Exception is: ".$e->getMessage()."<br/>";}?>updown-2 Hayley Watson ¶2 years agoRemember that Exceptions are also objects and can be handled as such; they can be constructed in and returned as values from functions, passed as arguments to other functions, and examined before being thrown. You don't have to throw it as soon as you have constructed it (the stack trace will of course reflect the moment the Exception was constructed, not the moment it was thrown).You might, for example, want to collect additional information to include in YourException but you don't want to clutter up the YourException class or the code containing the "throw" statement by collecting the information there. Or you might want to do something (such as logging) with each Exception that is thrown from a certain region (catch it, pass it to the logging function, then rethrow it).updown-2 Tom Polomsk ¶1 year agoContrary to the documentation it is possible in PHP 5.5 and higher use only try-finally blockswithout any catch block.updown-4 alex dowgailenko [at] g mail . com ¶5 years agoIf you use the set_error_handler() to throw exceptions of errors, you may encounter issues with __autoload() functionality saying that your class doesn't exist and that's it.If you do this:<?phpclass MyException extends Exception{}class Tester{public function foobar(){try{$this->helloWorld();} catch (MyException $e) {throw new Exception('Problem in foobar',0,$e);}}protected function helloWorld(){throw new MyException('Problem in helloWorld()');}}$tester = new Tester;try{$tester->foobar();} catch (Exception $e) {echo $e->getTraceAsString();}?>The trace will only show $tester->foobar() and not the call made to $tester->helloWorld().In other words, if you pass a previous exception to a new one, the previous exception's stack trace is taken into account in the new exception.updown-9 hartym dot dont dot like dot spam at gmail dot com ¶8 years ago@serenity: of course you need to throw exception within the try block, catch will not watch fatal errors, nor less important errors but only exceptions that are instanceof the exception type you're giving. Of course by within the try block, i mean within every functions call happening in try block.For example, to nicely handle old mysql errors, you can do something like this:<?phptry{$connection = mysql_connect(...);if ($connection === false){throw new Exception('Cannot connect do mysql');}/* ... do whatever you need with database, that may mail and throw exceptions too ... */mysql_close($connection);}catch (Exception $e){/* ... add logging stuff there if you need ... */echo "This page cannot be displayed";}?>By doing so, you're aiming at the don't repeat yourself (D.R.Y) concept, by managing error handling at only one place for the whole.ajax++mssql实现的ajax无刷新聊天室，支持html web编辑器。