Regras de resolução de nomes
Eli had a great idea with his code, however it started spewing tons of exceptions because of notices.
Here is a slightly different one.
<?php
set_error_handler(create_function('$x, $y', 'throw new Exception($y, $x);'), E_ALL & ~E_NOTICE);
?>
Exceções
PHP 5 tem um modelo de exceção similar ao de outras linguagens de programação. Uma exceção pode ser disparada (thrown), ou pega (caught ou "catched") no PHP. Código pode ser rodeado em um block try, para facilitar a captura de exceções em potencial. Cada bloco try, deve ter pelo menos um bloco catch correspondente. Vários blocos catch pode ser usado para pegar diferentes classes de exceções. A execução normal (quando nenhuma exceção é disparada dentro de um bloco try ou quando um catch compatível com a classe da exceção disparada não estiver presente) continuará após o último bloco catch definido na seqüência. Exceções podem ser disparadas (ou re-disparadas) dentro de um bloco catch.
Quando uma exceção é disparada, código logo após à instrução não será executada, e o PHP tentará achar o primeiro bloco catch correspondente à exceção disparada. Se uma exceção não for pega, um Erro Fatal do PHP será lançado com uma mensagem "Uncaught Exception ...", a não ser que um tratador tenha sido definido com set_exception_handler().
Exemplo #1 Disparando uma Exceção
<?php
function inverse($x) {
if (!$x) {
throw new Exception('Division by zero.');
}
else return 1/$x;
}
try {
echo inverse(5) . "\n";
echo inverse(0) . "\n";
} catch (Exception $e) {
echo "Exceção pega: ", $e->getMessage(), "\n";
}
// continua a execução
echo 'Hello World';
?>
O exemplo acima irá imprimir:
0.2 Exceção pega: Division by zero. Hello World
Exemplo #2 Exceções aninhadas
<?php
class MyException extends Exception { }
class Test {
public function testing() {
try {
try {
throw new MyException('foo!');
} catch (MyException $e) {
/* rethrow it */
throw $e;
}
} catch (Exception $e) {
var_dump($e->getMessage());
}
}
}
$foo = new Test;
$foo->testing();
?>
O exemplo acima irá imprimir:
string(4) "foo!"
Herdando Exceções
Uma classe de exceção definida pelo usuário pode ser criada herdando a classe Exception. Os membros e propriedades abaixo mostram o que é acessível a partir da classe filha que deriva da Exception.
Exemplo #3 A classe nativa Exception
<?php
class Exception {
protected $message = 'Unknown exception'; // Mensagem da exceção
protected $code = 0; // Código da exceção definido pelo usuário
protected $file; // Arquivo gerador da exceção
protected $line; // Linha geradora da exceção
function __construct(string $message=NULL, int code=0);
final function getMessage(); // Mensagem da exceção
final function getCode(); // Código da exceção
final function getFile(); // Arquivo gerador
final function getTrace(); // um array com o backtrace()
final function getTraceAsString(); // String formatada do trace
/* Sobrecarregável */
function _toString(); // String formatada para ser mostrada
}
?>
Se uma classe herda da classe Exception e redefine o construtor, é altamente recomendado que o mesmo chame parent::__construct() para garantir que todas as informações disponíveis sejam devidamente atribuídas. O método __toString() pode ser sobrecarregado para permitir uma saída personalizada quando o objeto é apresentado como string.
Exemplo #4 Herdando a classe Exception
<?php
class MyException extends Exception {
/* Redefine a exceção para que a mensagem não seja opcional */
public function __construct($message, $code = 0) {
// coisas personalizadas que você queira fazer
// ...
/* Garante que tudo é atribuído corretamente */
parent::__construct($message, $code);
}
/* Representação do objeto personalizada no formato string */
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "Uma função personalizada para esse tipo de exceção\n";
}
}
/**
* Cria uma classe para testar a exceção
*/
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:
// dispara exceção personalizada
throw new MyException('1 é um parâmetro inválido', 5);
break;
case self::THROW_DEFAULT:
// dispara a padrão
throw new Exception('2 não é permitido como parâmetro', 6);
break;
default:
// Nenhuma exceção, objeto será criado.
$this->var = $avalue;
break;
}
}
}
// Exemplo 1
try {
$o = new TestException(TestException::THROW_CUSTOM);
}
catch (MyException $e) { /* Será pega */
echo "Pegou minha exceção\n", $e;
$e->customFunction();
}
catch (Exception $e) { /* Ignorado */
echo "Pegou Exceção Padrão\n", $e;
}
var_dump($o); /* continua execução */
echo "\n\n";
// Exemplo 2
try {
$o = new TestException(TestException::THROW_DEFAULT);
}
catch (MyException $e) { /* Tipos não batem */
echo "Pegou minha exceção\n", $e;
$e->customFunction();
}
catch (Exception $e) { /* Será pega */
echo "Pegou Exceção Padrão\n", $e;
}
var_dump($o); /* continua execução */
echo "\n\n";
// Exemplo 3
try {
$o = new TestException(TestException::THROW_CUSTOM);
}
catch (Exception $e) { /* Será pega */
echo "Default Exception caught\n", $e;
}
var_dump($o); /* continua execução */
echo "\n\n";
// Exemplo 4
try {
$o = new TestException();
}
catch (Exception $e) { /* Ignorada, nenhuma exceção */
echo "Default Exception caught\n", $e;
}
var_dump($o); /* continua execução */
echo "\n\n";
add a note
User Contributed NotesExceções
Tim Gallagher
08-Apr-2008 06:41
08-Apr-2008 06:41
i dot crash17 at gmail dot com
05-Apr-2008 06:50
05-Apr-2008 06:50
As a response to Anonymous on 28-Dec-2007 07:25, please, remember that creating lots of MyXExtension classes is wrong if and only if your object oriented model is not well designed.
One should (I even think MUST) create as many custom Exception extentions as the design needs, because every different type of exception requires (or will require, even if we haven't think about it) a different response, from showing different messages to the user, to log error messages or even kill the script.
Forwarding can become confusing if you are using a big number of classes and packages, and is useless if you are using few (unless you are too lasy to write 3, 5 or 10 includes and their respective Exception classes).
Remember that object orientation was created to give more semantics to the programming code so the programmer understands better what is written without having to excecute the code, so don't do things that go against that, which is the cool thing about object orientation.
Eli Sand
31-Mar-2008 07:55
31-Mar-2008 07:55
There's been a few pieces of code already to show how to convert normal PHP errors in to exceptions, but if you want a simple single line you can put somewhere, try this:
<?php
set_error_handler(create_function('$x, $y', 'throw new Exception($y, $x);'));
?>
It doesn't get any easier than that. The only catch is this must be executed in the global scope. That means you can't embed this in a class for example. Just add it near the beginning of your entire script (where you include() files for example) and that should be it! Just make sure to catch the exceptions thrown, or set a default exception handler.
michael dot ochs at gmx dot net
21-Mar-2008 12:44
21-Mar-2008 12:44
Actually it isn't possible to do:
<?php
someFunction() OR throw new Exception();
?>
This leads to a T_THROW Syntax Error. If you want to use this kind of exceptions, you can do the following:
<?php
function throwException($message = null,$code = null) {
throw new Exception($message,$code);
}
someFunction() OR throwException();
?>
chugadie dot geo at yahoo dot com
05-Mar-2008 07:40
05-Mar-2008 07:40
@webmaster at asylum-et dot com
What Mo is describing is bug 44053 (http://bugs.php.net/bug.php?id=44053) in which exceptions cannot be caught if you are using a custom error handler to catch warnings, notices, etc.
webmaster at asylum-et dot com
15-Feb-2008 05:26
15-Feb-2008 05:26
According to Mo PDO exeptions do not currently extend the base Exception class and will not be caught by try {...} catc...
I am unsure what version that pertains to but I am running Windows XP SP 2, Apache 2.2.4.0, PHP 5.2.5.5 and it seems to work just fine.
See the code below.
<?php
$user='username here';
$pass='user pass here';
$dbase='database name here';
try {
$dbh = new PDO('mysql:host=localhost;dbname='.$dbase, $user, $pass);
echo 'Connection opened';
} catch (Exception $e) {
die("Error!: " . $e->getMessage() . '<br/>'."\n");
}
?>
Outputs:
Error!: SQLSTATE[28000] [1045] Access denied for user 'username here'@'localhost' (using password: YES)
Error!: SQLSTATE[28000] [1045] Access denied for user 'username here'@'localhost' (using password: NO)
Error!: SQLSTATE[42000] [1049] Unknown database 'database name here'
These are exactly the errors I would expect to see so my guess is that in one of the versions between what Mo had been using and current this issue has been fixed.
Mo
30-Dec-2007 03:44
30-Dec-2007 03:44
Note that PDO exceptions do not currently extend the base Exception class, and so will not be caught by:
try
{
...
} catch(Exception $e)
{
...
}
There are only two ways to handle PDO exceptions: by specifically catching PDOException, or by using an uncaught exception handler.
omnibus at omnibus dot edu dot pl
04-Dec-2007 12:11
04-Dec-2007 12:11
Just 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 helps
Jason
14-Nov-2007 07:36
14-Nov-2007 07:36
If you are wondering how to catch an include error and throw an exception, you can do so by doing:
<?php
try {
if(!@include('/path/to/file.php')) {
throw new Exception('Failed to load blabla');
}
}
catch(Exception $e) {
print $e->getMessage();
}
?>
This is helpful for people with custom Exception handlers that need to escape the default warning.
Too bad you can't, without using this method, catch the exception..
If you insist on using require() instead, you must understand that include() and require() are identical in all ways, except that the way they handle errors - require throws E_FATAL when the file isn't found, include issues E_WARNING, that's the only difference!
frank at netventures dot com dot au
08-Nov-2007 12:43
08-Nov-2007 12:43
If you are going to use multiple catches within a try-catch then do not forget the stacking order of those catches!
This is important as any classes that extend the Exception class, like MyException in example 20.3, will be caught in the Exception case. This is because your newly extended class also has a class type of Exception. This baffled me for awhile as the examples here worked but mine didn't because my first catch was trying to catch Exception.
Example:
<?php
/**
* My1Exception extends Exception
* My2Exception extends Exception
*/
/**
* This will always fall in the first exception
*/
try {
throw new My1Exception("My fail english? That's unpossible", 69);
} catch (Exception $e) {
print "Incorrect Exception";
} catch (My1Exception $e) {
print "Correct Exception but I won't be here";
} catch (My2Exception $e) {
print "Again, incorrect";
}
/**
* Whereas here, the catch stacking order was changed so our throw will cascade into the correct catch
*/
try {
throw new My1Exception("My cat's breath smells like cat food", 69);
} catch (My2Exception $e) {
print "Incorrect Exception";
} catch (My1Exception $e) {
print "Correct Exception and I WILL be printed";
} catch (Exception $e) {
print "Again, incorrect";
}
?>
So, ALWAYS keep the Exception catch block at the bottom, then any of the other extended exceptions that extend from Exception, then any of your other extended exceptions that extend from those extended exceptions, etc
hartym dot dont dot like dot spam at gmail dot com
18-Oct-2007 01:41
18-Oct-2007 01:41
@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:
<?php
try
{
$connection = mysql_connect(...);
if ($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.
serenity at exscape dot org
23-Aug-2007 01:20
23-Aug-2007 01:20
WOWA: You certainly do *not* need to throw an exception within the try block, that was just an example.
The only difference from JavaScript is that you need to add a class to catch (i.e. catch (Exception $e) instead of catch (e)).
Example:
<?php
try
{
// Code that might fail
}
catch (Exception $e)
{
echo "Caught exception: " . $e->getMessage();
// Or ErrorFunc(...) or whatever you'd like to do
}
?>
Jouni
20-Jun-2007 10:59
20-Jun-2007 10:59
If you are having troubles with exceptions and you are using eAccelerator, it is because of an eAccelerator v. 0.9.5 bug. See http://www.eaccelerator.net/ticket/242 for more information. I posted this here so that other eAccelerator users can save their time.
peter dot goodman at gmail dot com
15-Jun-2007 04:52
15-Jun-2007 04:52
I've found that exception destructors are not called unless the exception is caught.
I've created a simple solution to this problem (calling __destruct() from __toString() ) and have written up a lengthy article detailing one good use case for this method at http://ioreader.com/2007/06/14/taking-advantage-of-exceptions-in-php5/
Also, one of the useful things about using a destructor as a clean up method is that it is called at the end of a catch statement.
jon at hackcraft dot net
08-Jun-2007 02:00
08-Jun-2007 02:00
Hi corrupted_wise.
Your method works, but has a disadvantage in mixing two different error-handling methods.
There is clarity to be had in just using set_error_handler or just using try...catch (I recommend the latter).
If the code you want to avoid using is further inside the same try block than the code that could throw the exception (or called by code in the same block) then it won't be called in the case of the try block being exited due to an error. Therefore there is no need to use set_error_handler.
corrupted_wise at yahoo dot com
01-May-2007 01:37
01-May-2007 01:37
There was a certain section of my code that I needed to completely ignore if it failed. So I trapped it all in a try/catch and utilized the set_error_message, which in essence is like a pseudo-goto clutch. The reason for it all was if it failed during the code, I didn't want it to execute the rest of the respective section but continue outside of it. In the hopes it might help someone else out, here's what I did.
I'm using PHP 5.2.1
<?php
....
try {
set_error_handler(create_function('', "throw new Exception(); return true;"));
...code...
} catch(Exception $e) {
}
restore_error_handler();
?>
jon at hackcraft dot net
24-Jan-2007 06:52
24-Jan-2007 06:52
Further 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.
http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization and my own http://www.hackcraft.net/RAII/ describe this.
romain dot boisnard at gmail dot com
16-Jan-2007 06:43
16-Jan-2007 06:43
If you need a Java-like exception with a sort of "Throwable" cause to report the whole stackTrace, you can use this class I wrote and I release under the LGPL GNU Lesser General Public Liscence.
It looks more or less like the original PHP "Exception" but you might want to change the formatting of the returned string in the two last functions. Enjoy :)
<?php
/* Author : Romain Boisnard */
/* Liscenced under the LGPL GNU Lesser General Public Liscence, report the actual liscence for details.
/* LinkedException */
// Java-like exception with a cause
class LinkedException extends Exception {
private $cause;
function __construct($_message = null, $_code = 0, Exception $_cause = null) {
parent::__construct($_message, $_code);
$this->cause = $_cause;
}
public function getCause() {
return $this->cause;
}
public function getStackTrace() {
if ($this->cause !== null) {
$arr = array();
$trace = $this->getTrace();
array_push($arr, $trace[0]);
unset($trace);
if (get_class($this->cause) == "LinkedException") {
foreach ($this->cause->getStackTrace() as $key => $trace) {
array_push($arr, $trace);
}
}
else {
foreach ($this->cause->getTrace() as $key => $trace) {
array_push($arr, $trace);
}
}
return $arr;
}
else {
return $this->getTrace();
}
}
public function showStackTrace() {
$htmldoc = "<p style=\"font-family: monospace; border: solid 1px #000000\"><span style=\"font-weight: bold; color: #000000;\">An exception was thrown :<br/></span>";
$htmldoc.= "Exception code : $this->code<br/>";
$htmldoc.= "Exception message : $this->message<br/>";
$htmldoc.= "<span style=\"color: #0000FF;\">";
$i = 0;
foreach ($this->getStackTrace() as $key => $trace) {
$htmldoc.= $this->showTrace($trace, $i);
$i++;
}
$htmldoc.= "#$i {main}<br/>";
unset($i);
$htmldoc.= "</span></p>";
return $htmldoc;
}
private function showTrace($_trace, $_i) {
$htmldoc = "#$_i ";
if (array_key_exists("file",$_trace)) {
$htmldoc.= $_trace["file"];
}
if (array_key_exists("line",$_trace)) {
$htmldoc.= "(".$_trace["line"]."): ";
}
if (array_key_exists("class",$_trace) && array_key_exists("type",$_trace)) {
$htmldoc.= $_trace["class"].$_trace["type"];
}
if (array_key_exists("function",$_trace)) {
$htmldoc.= $_trace["function"]."(";
if (array_key_exists("args",$_trace)) {
if (count($_trace["args"]) > 0) {
$args = $_trace["args"];
$type = gettype($args[0]);
$value = $args[0];
unset($args);
if ($type == "boolean") {
if ($value) {
$htmldoc.= "true";
}
else {
$htmldoc.= "false";
}
}
elseif ($type == "integer" || $type == "double") {
if (settype($value, "string")) {
if (strlen($value) <= 20) {
$htmldoc.= $value;
}
else {
$htmldoc.= substr($value,0,17)."...";
}
}
else {
if ($type == "integer" ) {
$htmldoc.= "? integer ?";
}
else {
$htmldoc.= "? double or float ?";
}
}
}
elseif ($type == "string") {
if (strlen($value) <= 18) {
$htmldoc.= "'$value'";
}
else {
$htmldoc.= "'".substr($value,0,15)."...'";
}
}
elseif ($type == "array") {
$htmldoc.= "Array";
}
elseif ($type == "object") {
$htmldoc.= "Object";
}
elseif ($type == "resource") {
$htmldoc.= "Resource";
}
elseif ($type == "NULL") {
$htmldoc.= "null";
}
elseif ($type == "unknown type") {
$htmldoc.= "? unknown type ?";
}
unset($type);
unset($value);
}
if (count($_trace["args"]) > 1) {
$htmldoc.= ",...";
}
}
$htmldoc.= ")<br/>";
}
return $htmldoc;
}
}
?>
dexen at google dot me dot up
18-Sep-2006 03:45
18-Sep-2006 03:45
Summary:
* use destructors to perform a cleanup in case of exception.
PHP calls method __destruct() on instance of class when variable storing the instance goes out-of-scope (or gets unset). This works for function leave by Exception, aside of plain return. (same as for C++, AFAIK)
aFunction() {
$i = new LockerClass();
throw new MinorErrorEx('Warn user & perform some other activity');
// $i->__destruct() gets called before stack unwind begins, unlocking whatever get locked by new LockerClass();
return $bar;
}
(A lengthy) example:
Let's say you need to perform a series of operaions on SQL database that should not get disrupted. You lock the tables:
<?php
function updateStuff() {
DB::query('LOCK TABLES `a`, `b`, `c` WRITE');
/* some SQL Operations */
someFunction();
/* more SQL Operations */
DB::query('UNLOCK TABLES');
} ?>
Now, let's supouse that someFunction() may throw an exception. This would leave us with the tables locked, as the second DB::query() will not get called. This pretty much will cause the next query to fail. You can do it like:
<?php
function updateStuff() {
DB::query('LOCK TABLES `a`, `b` WRITE');
/* some SQL Operations */
try {
someFunction(); }
catch ( Exception $e ) {
DB::query('UNLOCK TABLES');
throw $e;
}
/* more SQL Operations */
DB::query('UNLOCK TABLES')
} ?>
However, this is rather ugly as we get code duplication. And what if somebody later modifies updateStuff() function in a way it needs another step of cleanup, but forget to add it to catch () {}? Or when we have multiple things to be cleaned up, of which not all will be valid all the time?
My solution using destructor: i create an instance of class DB holding a query unlocking tables which will be executed on destruction.
<?php
function updateStuff() {
$SQLLocker = DB::locker( /*read lock list*/array('a', 'b'), /*write lock list*/array('b') );
/* some SQL Operations */
someFunction();
/* $SQLLocker gets destructed there if someFunction() throws an exception */
DB::query('UNLOCK TABLES');
/* other SQL Operations */
/* $SQLLocker gets destructed there if someFunction() does not throw an exception */
}
class DB {
function locker ( $read, $write ) {
DB::query( /*locks*/);
$ret = new DB;
$ret->onDestruct = 'UNLOCK TABLES';
return $ret;
}
function _destructor() {
if ( $this->onDestruct )
DB::query($this->onDestruct);
}
}
?>
jazfresh at hotmail.com
08-Aug-2006 07:18
08-Aug-2006 07:18
Sometimes 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> $var) will match the given <classname> *or any of it's sub-classes*.
For example:
<?php
class DisplayException extends Exception {};
class FileException extends Exception {};
class AccessControl extends FileException {}; // Sub-class of FileException
class IOError extends FileException {}; // Sub-class of FileException
try {
if(!is_readable($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 $e) {
// This block will catch FileException, AccessControl or IOError exceptions, but not Exceptions or DisplayExceptions.
echo "File error: ".$e->getMessage();
exit(1);
}
?>
Corollary: If you want to catch *any* exception, no matter what the type, just use "catch(Exception $var)", because all exceptions are sub-classes of the built-in Exception.
linus at flowingcreativity dot net
19-Jul-2006 11:06
19-Jul-2006 11:06
Here is a basic example of a way to mimick the convenience of exception handling in PHP4:
<?php
do {
if (!$test_condition) {
$error = 'test condition failed';
break;
}
if (!test_function()) {
$error = 'test function failed';
break;
}
echo 'success!';
} while (false);
if (isset($error)) {
echo $error;
}
?>
Obviously this falls far short of PHP5 real exception handling in terms of normalisation. Also, $error won't propogate up the call stack like a real exception (i.e. test_function() can't itself throw an exception, nor call 'break'). But for me, the most important thing about exception handling is to be able to run through code and deal with errors separately, and not have to have a million nested IFs. Compare that code to this:
<?php
if (!$test_condition) {
$error = 'test condition failed';
} elseif (!test_function()) {
$error = 'test function failed';
} else {
echo 'success!';
}
if (isset($error)) {
echo $error;
}
?>
At first this seems no more cumbersome, but what if test_function took arguments that required complicated preparation? You would need a mess like this:
<?php
if (!$test_condition) {
$error = 'test condition failed';
} else {
$fooRes = mysql_query('SELECT foo FROM bar LIMIT 1');
$fooRow = mysql_fetch_assoc($fooRes);
if (!test_function($fooRow)) {
$error = 'test function failed';
} else {
echo 'success!';
}
}
?>
Obviously this could get out of hand quickly. In the first example, you can just prepare the argument before the 'if (!test_function($fooRow))', and on the same nesting level.
This method is also somewhat more flexible in that you can generate 'exceptions', and then deal with them much later (which may be desirable if they aren't really threatening). In PHP5, a catch block must always follow a try block directly.
tatarynowicz at gmail dot com
10-Jul-2006 03:26
10-Jul-2006 03:26
Carlos Konstanski: You can't directly extract previous lexical environment in non-functional languages.
What you probably _can_ do is to create a function that dumps the current lexical environment (to an external file or to stdout) and then use it to recreate past states.
function log_lex ($vars, $functions) {
$f = fopen('lex_env.log', 'a');
fwrite($f, serialize(array($vars, $functions, get_defined_constants(), debug_backtrace()));
fclose($f);
}
log_lex (get_defined_vars(), get_defined_functions());
Writing the parser/browser for dumps is the difficult part. Then just sprinkle the code with log_lex() and see how the program runs.
Sure, it works better in Lisp, but Lisp isn't supported on the webservers I work with, and making PHP more like Lisp would probably make it as popular as Lisp is.
fjoggen at gmail dot com
26-Apr-2006 10:58
26-Apr-2006 10:58
This code will turn php errors into exceptions:
<?php
function 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.
gerry03 at 4warding dot com
14-Nov-2005 06:39
14-Nov-2005 06:39
Good PHP5 article about exceptions. I have read quite a few now and this is the only one I've liked:
http://www.andreashalter.ch/phpug/20040115/
Carlos Konstanski
30-Sep-2005 07:17
30-Sep-2005 07:17
Being able to catch the exception up the call stack from where it is thrown is a good idea, in that it lets you handle the exception closer to where it ought to be handled - in the calling code. Not as good as common lisp though, where you can call a condition handler that resides up the stack without actually unwinding the stack. With this additional feature, you have the lexical environment at the point where the exception occured, combined with the relocation of the handler to a place where the lower-level function's failure can be addressed from the standpoint of the calling code.
Even so, this fluke of PHP that lets you place the try...catch block up the stack from the actual point of error could be used to implement a neat shift in error-handling architecture, where the caller gets to decide how to proceed after an error.
jd at wuputah dot com
07-May-2005 04:15
07-May-2005 04:15
PHP5 supports exception throwing inside a function, and catching it outside that function call. There is no mention of this in documentation but it works just fine, as tested by this sample code:
<?php
function exceptionFunction() {
throw new Exception("Throwing an exception!");
}
try {
exceptionFunction();
} catch (Exception $e) {
echo "Exception caught!\n";
}
?>
The result in PHP 5.0.3 is "Exception caught!"
Further tests show that nested functions with exceptions, methods throwing exceptions, etc all work the same way. This is like declaring all classes (or methods) in Java as "class ClassName throws Exception". While I consider this a good thing, you should be aware that any thrown exception will propagate up your stack until it is either caught or runs out of stack.
php5 at grapio dot nl
07-Oct-2004 03:16
07-Oct-2004 03:16
The base exception class, which is build in PHP5 has also a function getLine(). This is as expected if you look at the class define. But it is not noticed there.
I had just this code:
<?php
try
{
throw new Exception("test")
}
catch (Exception $e)
{
echo $e->getLine()
}
?>
And this worked.