Req #26789 [Com]: NullPointerException desired
Edit report at https://bugs.php.net/bug.php?id=26789&edit=1
ID: 26789
Comment by: nikic@php.net
Reported by: davidc at blesys dot com
Summary: NullPointerException desired
Status: Wont fix
Type: Feature/Change Request
Package: *General Issues
Operating System: (doesn't apply)
PHP Version: 5.0.0b3 (beta3)
Block user comment: N
Private report: N
New Comment:
@3leven11: This will definitely not be a NullPointerException (because PHP doesn't have
pointers and because PHP does not throw exceptions from core), but it could be changed to an
E_RECOVERABLE error. You wouldn't be able to conveniently catch it, but you could still handle
it (e.g. display an error page rather than just a WSOD). It think @ircmaxell wanted to make it a
RECOVERABLE, but I don't know what the state on that currently is.
Previous Comments:
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[2012-10-20 10:21:47] 3leven11 at gmail dot com
@nikic, I completely understand what you are saying, and I have indeed
altered my code to pass the exception up the chain to the callers of the sub class
constructors. I still think a NullPointerException over a Fatal Error would be
nice, but that is just my Java developer way of thinking.
I appreciate you taking the time to respond.
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[2012-10-20 09:52:08] pajoye@php.net
In addition to Niki's comment, there is no such thing like pointer in PHP.
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[2012-10-20 08:37:27] nikic@php.net
@3leven11: I have a hard time understanding your particular situation. I mean, if you can't
connect to the database, then you should throw an exception *at that point* (PDO actually does it
for you, but you choose to silence the exception).
If you need this to check for such error conditions then I would highly recommend you to just throw
an exception as the error occurs rather than passing NULLs around everywhere. That's basically
the "error code" way of handling errors (in your case even without the code) and it indeed
involves checking every single call. That's why people mostly prefer throwing exceptions.
------------------------------------------------------------------------
[2012-10-20 04:12:14] 3leven11 at gmail dot com
I find the comment by derick@php.net to be very unhelpful.
Testing an object for null every time you use it while being a solution, is a
very primitive way of ensuring your application does not crash in an ungraceful
manner. Exception handling, is a much more efficient way of ensuring your
application can continue running when abnormal events occur.
While I agree that it is up to the developer to handle if an object is null, I
do see a case where checking for null is an unnecessary performance hit on any
application. And could be avioded by the implementation of a
NullPointerException in PHP. Handling errors in code is up to the developers,
but they can only handle them the best way they know how, with the tools
provided to them.
Take the example of an object that you rarely expect to be null, like a PDO
object. I expect my database to be available 99.9% of the time, are you really
implying that it is better practice to test for null every I use this object
rather than enclose my use of a PDO object within a try catch block, handling
any exception that may arise?
example code:
// base class
namespace lib\translator;
use lib\database as db;
class EntityTranslator {
protected $dbConn;
public function __construct() {
try {
$this->dbConn = db\Database::getInstance();
}
catch(\PDOException $e) {
// do some error logging here
}
}
}
// subclass
namespace lib\translator;
use lib\entity as entity;
class OrderRequestTranslator extends EntityTranslator {
public function __construct() {
parent::__construct();
}
public function createOrderRequest() {
$request = new entity\Request();
try {
$stmt = $this->dbConn->prepare("CALL createRequest()");
$stmt->execute();
$rowCount = $stmt->rowCount();
if ($rowCount == 1) {
$row = $stmt->fetch(\PDO::FETCH_ASSOC);
// do stuff with the data here
}
return $request;
}
catch (\PDOException $pdoe) {
// do error logging here
}
catch (\Exception $ex) {
// do error logging here
}
}
}
So in the above example, if there is an exception while connecting to the
database, which as I pointed out I expect to very rare, and it may actually
never happen, that before issuing the call to $this->dbConn I should check if
$this->dbConn is null?
This is the perfect case for where my catch(\Exception $ex) {} block would be
perfect. I really never expect to be in that code, from my point of view, and
correct me if I am wrong, I have not coded my application in an incorrect way,
except for the fact that PHP has no NullPointerException.
------------------------------------------------------------------------
[2012-03-13 22:22:56] me at joshsera dot com
The point of an NPE is so you can enclose code in a try/catch block instead of
wrapping every statement in an if that tests for null. It makes for more readable
code.
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