This is more just for documentation, since I've already solved the issue, but it was subtle and difficult enough to debug that I thought it would be useful in the public sphere.
The issue was that I had a try/catch block in an object method that just wasn't working. The reduced example is in two files, which look like this:
TestClass.php:
<?php
//TestClass.php
namespace MyTest;
class TestClass {
public function __construct() {
\e("Initializing object");
try {
\e("Trying object exception");
\throwTestException("Failing gracefully in object");
\e("After exception");
} catch (Exception $e) {
\e($e->getMessage());
}
\e("After object init exception");
}
}
?>
Main.php:
<?php
//Main.php
function e($str) { echo "\n$str"; }
function throwTestException($msg) {
throw new RuntimeException($msg);
}
require "TestClass.php";
e("Beginning");
try {
e("First try");
throwTestException("Failing gracefully first");
e("After exception");
} catch (Exception $e) {
e($e->getMessage());
}
e("Ending");
e('');
e('Beginning object test');
new \MyTest\TestClass();
e('Ending object test');
?>
The expected result on loading Main.php was this:
Beginning
First try
Failing gracefully first
Ending
Beginning object test
Initializing object
Trying object exception
Failing gracefully in object
After object init exception
Ending object test
What I actually got was something like this:
Beginning
First try
Failing gracefully first
Ending
Beginning object test
Initializing object
Trying object exception
Fatal Error: Uncaught Exception: Failing gracefully in object......
As you can see, the exception was not being caught. I tried all sorts of things and just couldn't figure out why it wasn't being caught. And then.... (See answer below)
I realized it was a namespace issue. Because I had declared TestClass within the namespace MyTest, and throwTestException in the global namespace, my reference to Exception within the class method was tacitly resolving to \MyTest\Exception and thus NOT matching the actual exception being thrown, \RuntimeException. And since I wasn't actually trying to instantiate the exception from within the namespace, no "Unknown Class" errors emerged to reveal what was happening.
The solution, then, was simply to properly resolve the exception class I was trying to catch:
catch(\Exception $e) { .... }
To be fair, this became obvious as I built my highly reduced example. It wasn't obvious initially because the exception I was expecting to catch was being generated by the class's superclass (which was the SQLite3 class). Thus, I didn't have to worry about the namespace when generating the exception, and all I was thinking about when catching it was to use the most general form of exception, Exception. And again, since I wasn't instantiating that exception -- only matching against it in a catch block --, I didn't get any notices that it was unresolved.
Related
I want to catch a specific Exception and handle it properly. However, I have not done this before and I want to do it in the best way.
Will it be correct to create a separate class something like
class HandleException extends Exception
{
//my code to handle exceptions;
}
and in it have different methods handling the different exception cases? As far as I understand, the Exception class is like an "integrated" class in php so it can be extended and if an Exception is caught it is not obligatory to terminate the flow of the program?
And, an instance of this class will be created when an exception is caught? Sth. like
catch ( \Exception $e ) {
$error = new HandleException;
}
You CAN extend the basic Exception object with your own, to provide your own exception types, e.g.
class FooExcept extends Exception { .... }
class BarExcept extends Exception { .... }
try {
if ($something) {
throw new FooExcept('Foo happened');
} else if ($somethingelse) {
throw new BarExcept('Bar happened');
}
} catch (FooExcept $e) {
.. foo happened, fix it...
} catch (BarExcept $e) {
... bar happened, fix it ...
}
If an Exception is caught, then the program DOESN'T necessarily have to abort. That'd be up to the exception handler itself. But if an exception bubbles always back up to the top of the call stack and ISN'T caught, then the entire script will abort with an unhandled exception error.
From the manual
Multiple 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.
So you can do something like this:
try {
// some code
} catch ( HandleException $e ) {
// handle sthis error
} catch ( \Exception $e ) {
// handle that error
}
This will handle different exceptions. You can also use the finally keyword with newer versions of PHP.
I was getting an error about an exception thrown in a __toString() method in a class of mine, even though there was a try...catch() in there. I did some tracking down and it turns out an object within my instance was throwing an exception in its __toString(), which meant that it wasn't being caught by the containing class' catch!
I wrote some test code as a demonstration:
class test {
public function __toString() {
try {
$b = new b();
echo (string)$b;
} catch (exception $e) {
return (string)$e;
}
}
}
class b {
public function __toString() {
throw new Exception ("test");
}
}
$test = new test();
echo $test;
I had thought that exceptions always "bubbled up" through the code until they were caught or made it all the way out.
Is there any workaround for this? The instance within my class is from a library; I don't know if I can maintainably modify it to have a catch in its own __toString().
Per PHP's __toString() section in the magic methods docs:
Warning
You cannot throw an exception from within a __toString() method. Doing
so will result in a fatal error.
When executing the code snippet you gave you get a message that says the same thing:
PHP Fatal error: Method b::__toString() must not throw an exception
There's a feature request here to support this, which states that in current state of things it would be hard to implement.
Having said all that, the proper way to fix this is to submit a patch to your upstream library to not throw exceptions from that method.
If that's not possible, the workaround for you is instead of:
echo (string)$b;
write
echo $b->__toString();
In which case you can catch the exception as you expect.
What does $previous in the Exception constructor argument denote? How could I use it?
class MyException extends \Exception {
private $message;
private $code;
public function __construct($message,$code,\Exception $previous=null){
$this->message = $message;
$this->code = isset($code) ? $code : 0;
parent::__construct($message,$code,$previous);
}
}
I didn't find anything in the API Doc
If you throw an exception because you caught an exception, you can add the original exception as $previous. That means you can actually "nest" exceptions:
try {
throw new FooException('Foo exception');
} catch (FooException $e) {
$code = 1;
throw new BarException('Bar exception', $code, $e);
}
You can then loop over the exception "stack" instead of just the exception caught, providing you with more context.
while($e instanceof \Exception) {
echo $e->getMessage();
$e = $e->getPrevious();
}
Now, you would probably use this if you're implementing a library that can throw an exception, but you'd like to wrap that exception in your own. That way, your clients' code only needs to know of your exceptions, and not that of the exceptions that the dependencies of your code has, while not losing any kind of information.
the reason is that PHP 5.3 introduces nested exceptions as a default part of the PHP base Exception class. While the above code will work, if you are utilizing PHP 5.3, you can pass any previous exception as a third argument , and use the Exception::getPrevious() method to get a previously raised exception.
argument of a previous exception, allowing you to nest the exceptions. When preparing to log your exception, you can opt to iterate through any possible previously thrown and nested exceptions, and log any of the data you need.
What is nesting? Nesting is the ability to catch a particular exception, create a new exception object to be thrown with a reference to the original exception. This then allows the caller access to both the exception thrown from within the consumed library of the more well known type, but also access to the exception that originated this exceptional behavior as well.
Why is this useful? Typically, this is most useful in code that consumes other code that throws exceptions of its own type. This might be code that utilizes the
for more
http://www.brandonsavage.net/exceptional-php-nesting-exceptions-in-php/
I want to catch an exception that is thrown by the Google API PHP library, but for some reason it generates a 'Fatal error: uncaught exception' before reaching my catch block.
In my app I have something like this:
try {
$google_client->authenticate($auth_code);
} catch (Exception $e) {
// do something
}
This is Google_Client's authenticate():
public function authenticate($code)
{
$this->authenticated = true;
return $this->getAuth()->authenticate($code);
}
The authenticate($code) above is Google_Auth_OAuth2::authenticate(), which at some point throws the exception:
throw new Google_Auth_Exception(
sprintf(
"Error fetching OAuth2 access token, message: '%s'",
$decodedResponse
),
$response->getResponseHttpCode()
);
If I put a try/catch block in the Google_Client's authenticate, it catches the exception, but without it the program just dies instead of reaching the main try/catch block from my app.
As far as I know this shouldn't be happening. Any ideas?
The problem was that the try/catch block was in a namespaced file and PHP requires you to use "\Exception". More info: PHP 5.3 namespace/exception gotcha
Example (taken from the link above):
<?php
namespace test;
class Foo {
public function test() {
try {
something_that_might_break();
} catch (\Exception $e) { // <<<<<<<<<<< You must use the backslash
// something
}
}
}
?>
I'm not sure how the structure of Google's API is, and I'm not a real fluent PHP programmer, but you're catching a specific exception type of Exception, with which Google's Google_Auth_Exception may not inherit from.
Therefore, since your try-catch block is looking for an exception that is a member of Exception and the Google_Auth_Exception is perhaps not a member of Exception, then your try catch block will miss it.
Try catching the specific exception. This has happened to me before in many different languages.
Edit
The link you posted inherits its exception from: Google/Auth/Exception
Google/Auth/Exception inherits its exception from: Google/Exception
Google/Exception extends Exception, which may, in this context be the Exception that your class is referring to.
It seems my justification for your try-catch block not catching an exception is completely wrong, but the wisdom could still be true. Try catching the specific exception, then use instanceof to see if PHP recognizes Google_Auth_Exception as a member of Exception.
I witnessed some strange behaviour regarding PHP's exception handling in a recent project. Case goes as follows.
In my app, I use namespaces. All classes are in individual source code files. The code relevant to this particular case, is spread over 3 classes.
The "outermost" class is a dispatcher (or router), which wraps the dispatch call inside a try-catch block. The dispatched request, calls a method in a third class, which runs code (wrapped in a try-catch block), which causes an exception.
Because I had omitted a use Exception; statement in the class where the error happens, the thrown exception trickles all the way back to the outermost layer (the dispatcher), where it is caught - causing me to scratch my head why the catch around the code causing the error isn't working.
To me this seems strange. Logically, PHP should in this situation (IMO) throw a Class not found exception/error, leading me to the actual error in my code, instead of trying to "stay alive" as long as possible.
Should this be filed as a bug, or is this expected behaviour?
Edit: Code example
File: class-a.php
<?php
namespace hello\world;
class classA {
protected $b;
public function __construct() {
$this->b = new \hello\world\classB();
}
public function doSomething() {
try {
$this->b->throwException();
} catch (Exception $e) {
}
}
}
File: class-b.php
<?php
namespace hello\world;
class classB
{
public function throwException() {
throw new \Exception("bar closed");
}
}
File: run.php
<?php
include 'class-a.php';
include 'class-b.php';
$a = new \hello\world\classA();
$a->doSomething();
ClassB throws an \Exception in ClassB::doSomething(), for which ClassA has a catch-clause, but because ClassA doesn't declare use Exception or catch (\Exception), the catch doesn't match and execution ends with a Uncaught exception error1. But in my opinion, it should cause a Class not found error.
I might be expecting too much of the permissive PHP compiler, but it would help in tracking down silly errors that should be easy for the compiler to spot.
1 If the $a->doSomething() in run.php was surrounded by a try..catch clause, the Exception would (or at least could) be caught there, since it trickles down the stack.
PHP's exception catching mechanism does not validate that the class you catch actually exists.
It exhibits the same behavior when using typehinting in functions, so I suspect it merely converts the exception/function type hint into a string or something and compares that with the type of the relevant object.
Whether this is a bug or not is questionable. Personally I think it should be classified as a bug, but PHP has all sorts of wonky behaviors :D