ID: 29736
Comment by: indeyets at gmail dot com
Reported By: hans at velum dot net
Status: Open
Bug Type: Feature/Change Request
Operating System: *
PHP Version: 5.0.1
New Comment:
I'll try to summarize:
there is no easy way to check if class implements some interface. This
is needed, when, for example, php-application has support for loading
external classes.
external classes have to implement some interface. And check for this
should happen BEFORE object creation. (for example, there might be a
need for some specific constructor syntax).
PHP 5.0 allows to do the following things:
1). $parent = get_parent_class("SomeClassName"). This would be
sufficient, if plugins _extend_ some base class. that's not our case -
wouldn't work for interfaces
2). if ($obj instanceof "SomeInterfaceName") {}. This would work, if we
could create object before the interface check. Wouldn't work for
non-existen objects
3). reflection API. it can do the thing, but overhead (both in code and
in resources) is too big
Previous Comments:
------------------------------------------------------------------------
[2004-08-19 02:43:04] [EMAIL PROTECTED]
The example was buggy, but the bug exists :)
php5 -r 'class Foo{} $f = unserialize("O:3:\"Foo\":0:{}");
var_dump(!($foo instanceof Bar));'
Bar could be a huge class, I dont want to load it just to check $f
wasnt a instance of it?
------------------------------------------------------------------------
[2004-08-19 02:40:32] hans at velum dot net
Well, no ... the problem that I am describing has nothing to do with
unserialize(). That was just an example that Sean posted that
illustrates how is_a() and instanceof differ. I apologize if that
wasn't clear.
You did reproduce the bug in your first example.
Simple reproduction:
<?php
$c = null;
print '$c instanceof PEAR_Error ? ' . ($c instanceof PEAR_Error);
?>
Will result in E_FATAL (no such class). That's the problem. is_a()
has no such limitations, but is now deprecated. This change
suggestion/request is asking for a way to check whether a variable is
an instance of a particular class/superclass/interface *without loading
that class/interface*.
Hope that makes it clearer.
-Hans
------------------------------------------------------------------------
[2004-08-19 01:28:46] [EMAIL PROTECTED]
Can't reproduce:
[EMAIL PROTECTED] /usr/src/PHP_5_0 $ php -r 'function __autoload($name) {
var_dump($name); } $x = NULL; var_dump($x instanceof test);'
make: `sapi/cli/php' is up to date.
string(4) "test"
Fatal error: Class 'test' not found in Command line code on line 1
[EMAIL PROTECTED] /usr/src/PHP_5_0 $ php -r 'function __autoload($name) {
var_dump($name); eval("class $name {}");} $x = NULL; var_dump($x
instanceof test);'
make: `sapi/cli/php' is up to date.
string(4) "test"
bool(false)
So the problem lies in unserialize() -> other bug
------------------------------------------------------------------------
[2004-08-18 16:31:23] hans at velum dot net
Description:
------------
[pasted from messages on internals@ list]
I like the new $obj instanceof ClassName way of checking class /
interface types, .... but this method does have one major drawback
compared to the old is_a() approach:
The class must be loaded in order to perform an instanceof check!
There are many situations where you do not want to have to load every
class to see whether a returned object is a class of that type. In
particular for driver classes, the current model requires loading
*every* possible driver in order to check to see which type of class
was returned.
is_a() works great, but has been deprecated and is now generating
E_STRICT errors.
Reproduce code:
---------------
[conributed by Sean Coates on internals@ list]
<?php
class Foo {}
$foo = unserialize('O:3:"Foo":0:{}');
echo '$foo is_a Foo? '. (is_a($foo, 'Foo') ? 'yes' : 'no') ."\n";
echo '$foo instanceof Foo? '. ($foo instanceof Foo ? 'yes' : 'no')
."\n";
?>
---- and ----
<?php
//class Foo {}
$foo = unserialize('O:3:"Foo":0:{}');
echo '$foo is_a Foo? '. (is_a($foo, 'Foo') ? 'yes' : 'no') ."\n";
echo '$foo instanceof Foo? '. ($foo instanceof Foo ? 'yes' : 'no')
."\n";
?>
Expected result:
----------------
$foo is_a Foo? yes
$foo instanceof Foo? yes
---- and ----
$foo is_a Foo? no
$foo instanceof Foo? no
Actual result:
--------------
$foo is_a Foo? yes
$foo instanceof Foo? yes
---- and ----
$foo is_a Foo? no
Fatal error: Class 'Foo' not found in
/home/sean/phpdoc/scripts/tmp/is_a.php on line 8
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=29736&edit=1
