Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

This is correct, the isset() checks if a variable is set or not. In your case it\'s simply not set (it will be set after __get() is executed on it once).

Sorry, but if you do that :
$o->a = 'foo';
echo isset($o->a) ? "yes\n" : "no\n";
Expected result was true, but actual result is false !
And $o->a is set !

Still not resolved, you still have to use the following code to access the properties:

$a = $o->a;
echo isset($a) ? "yes\n" : "no\n";

Another guy thought that it would be neat if there was a __isset magic method.

This works fine for me:

derick@kossu:~$ cat bug29917.php
<?php
        class oo {
                var $a;
        }

        $o = new oo;
        echo isset($o->a) ? "yes\n" : "no\n";
        $o->a = 'bar';
        echo isset($o->a) ? "yes\n" : "no\n";
?>
derick@kossu:~$ php bug29917.php
no
yes


Come up with a short example like mine that shows that it doesn't work. Just saying $o->a won't work doesn't help.

<?php

class OO
{
	private $array = array();

	function __construct() {}

	function __set($name, $value)
	{
		$this->array[$name] = $value;
	}

	function __get($name)
	{
		if (isset($this->array[$name]) == true)
			return null;
		else
			return $this->array[$name];
	}
}

$o = new oo();
$o->foo = 'bar';
echo (isset($o->foo) == true ? 'foo is set' : 'foo is not set');

#Expecting result
# => foo is set
#Real result
# => foo is not set

?>

If PHP provide __set() and __get() function in order to create property dynamicaly, PHP function like isset() MUST BE USED with these "dynamic" properties as usual.
So, in my example, isset() MUST return TRUE !! and not FALSE !!

No, you're wrong. The behavior you see is the correct behavior.

Can you explain where are wrong ???

A call to __set() create a property in the object (see documentation).
Event if this property is not a real member property for PHP language point of view, for the programers point of view, it is a property !

So, isset() MUST return true in my example.

What are difference between your example :

$o->a = 'bar';
echo isset($o->a) ? "yes\n" : "no\n";

And my example :

$o->foo = 'bar';
echo (isset($o->foo) == true ? 'foo is set' : 'foo is not set');

There is no difference ! Except that my foo property was created with a __set() call.

If the isset() function aren't going to work with properties accessed with a __get() call, then there should at least be a __isset() method that allows for custom isset()-handling. eg:

    <?php

    class Foo
    {
        private $bar = "bar";

        public function __isset ($prop)
        {
            if (isset($this->$prop)) {
                return TRUE;
            } else {
                return FALSE;
            }
        }
    }

    $foo = new Foo();

    echo isset($foo->bar) ? "yes\n" : "no\n";

    // Should be the same as

    echo $foo->__isset('bar') ? "yes\n" : "no\n";

    ?>

<?php

class foo implements arrayAccess
{
   private $array = array();

   function __construct() {}

   function __get($key)
   {
      return $this->offsetGet($key);
   }

   function __set($key, $value)
   {
      $this->offsetSet($key, $value);
   }

   function offsetExists($key)
   {
      return isset($this->array[$key]);
   }

   function offsetGet($key)
   {
      return $this->array[$key];
   }

   function offsetSet($key, $value)
   {
      $this->array[$key] = $value;
   }

   function offsetUnset($key)
   {
      unset($this->array[$key];
   }
}

$foo = new foo();

echo (isset($foo['bar']) == true ? 'set' : 'not set');
$foo['bar'] = 'bar';
echo (isset($foo['bar']) == true ? 'set' : 'not set');
echo $foo['bar'];

#Expected result :
# not set
# set
# bar
#Real result
# not set
# set
# bar
# !! GREAT !!

#Now, the same thing with __get() and __set()

unset($foo);
$foo = new foo();

echo (isset($foo->array) == true ? 'array is set' : 'array is not set');
echo (isset($foo->bar) == true ? 'bar is set' : 'bar is not set');
$foo->bar = 'bar';
echo (isset($foo['bar']) == true ? 'bar is set' : 'bar is not set');
echo $foo->bar;

#Expected result :
# array is set
# bar is not set
# bar is set
# bar
#Real result
# array is set # Ok !
# bar is not set # Ok !
# bar is not set # PROBLEM PROBLEM
# bar
# !! NOT GREAT !!

?>

It is abnormal !
isset() does not return the good value on property wich was set with __set() it is return the good value on property wich was set in the class,and isset() return the good value on value wich was set with offsetSet() method !!
It is a paradox !

I think that isset MUST return the same value in all case.

We'd need to all __get() for every non existing property then which would be worse than only a mahor slowdown.
Een a __exists() would'n help much because that, too. Would be very slow. The only way out would be to declare abstract properties as allowed by this patch:

http://marcus-boerger.de/php/ext/ze2/ze2-abstract-properties-20040803.diff.txt

The problem was not that __set() and __get() are slow.
The problem is that, if __get() and __set() are defined in an object, PHP becomes "unconsistent", that is to say that some functions like isset() have not these usual behavior if __get() and __set() are defined in an object.
And abstract properties is a very strange concept...
However, a __get() and __set() optimization is a good idea.

Fred.

PHP doesn't become inconsistent. It only doesn't allow to check for the presense of virtual proeprties using isset()/empty(). 

The problem is that we cannot allow the consistency because that would mean that we need to call __get() for every isset/empty property check where the property is no declared. Also defining a __exists has the same problem. Still we would need to call it for every non declared property. So that is both a major slow down which we cannot overcome by some __get/__set optimizations.