It should not be __isset,because isset() is not the same thing as empty()
Asked
Active
Viewed 6,974 times
7
user198729
- 61,774
- 108
- 250
- 348
4 Answers
17
As it says on this page:
__isset() is triggered by calling isset() or empty() on inaccessible properties.
There is no dedicated magic-method for empty()
If __isset() returns true, empty() will then invoke __get() to check the value of the property.
Inspire
- 2,052
- 15
- 14
-
So the result is always the same or `isset()` or `empty()` ? – user198729 Mar 12 '10 at 08:39
-
Yes, if your __isset method returns true, both empty() and isset() will return true. You probably should implement a "non-magic" method to do the check for empty(), and keep __isset only for isset() – Inspire Mar 12 '10 at 08:44
-
Hmm as a matter of fact, it seems empty() returns true if the __isset method returns false but isset() returns false in this case. If __isset returns true, they both return true (tested on PHP 5.3.0) – Inspire Mar 12 '10 at 08:48
-
So I guess it first calls `__isset`,then `__get`? – user198729 Mar 12 '10 at 08:51
-
That seems to be right and makes sense (I didn't write a __get method in my test code which must have been why empty() was always returning true). – Inspire Mar 12 '10 at 09:02
5
As an addition to Inspire's answer:
class Foo {
public function __isset($name) {
echo "public function __isset($name)\n";
return 'bar'===$name;
}
public function __get($name) {
echo "public function __get($name)\n";
return 'bar'===$name ? 0 : NULL;
}
}
$foo = new Foo;
echo empty($foo->foo) ? ' empty' : ' not empty', "\n";
echo empty($foo->bar) ? ' empty' : ' not empty', "\n";
the output is
public function __isset(foo)
empty
public function __isset(bar)
public function __get(bar)
empty
meaning for the first property (foo) empty() only invoked __isset() which returned false -> empty($foo->foo)===true
For the second property (bar) __isset() was invoked and it returned true. Then the property is fetched via __get() and interpreted as a boolean value (see http://docs.php.net/language.types.type-juggling). And since (bool)0 is false, empty() also returns true for empty($foo->bar)
VolkerK
- 95,432
- 20
- 163
- 226
0
I think in general you'll find that the following is the PHP equivalent:
isset($variable[0])
If, for example, the variable is a string, this would detect that the string was empty. It would work similarly for most primitive types (if not all).
Fenton
- 241,084
- 71
- 387
- 401
-
I want to know which magic function is called for `empty($this->attr)` – user198729 Mar 12 '10 at 08:36
