Re: [PHP5] paradox ? Bug ?

I think this basically sums up the problems of the current handling of existence-checking in overloaded objects: We have an object that has user-defined methods for getting and setting object properties (__get() and __set(), respectively). These methods get and set the properties in a private array (private: can only be access from within the object itself). Example (mostly stolen from php.net): <?php class Foo { // This array holds the properties private $elem = array(); // This method is automatically called when an // undefined (or inaccessible, as $array) property is // called. The name of the called property is the only // argument. public function __get ($prop) { if (isset($this->elem[$prop])) { return $this->elem[$prop]; } else { trigger_error("Oooops", E_USER_WARNING); } } // Same as before, but is called when setting a // property public function __set ($prop, $val) { $this->elem[$prop] = $val; } } // Instantiate the class $foo = new Foo(); // Check if $foo->bar ($foo->elem['bar']) is set if (isset($foo->bar)) { echo "\$bar is set\n"; } else { echo "\$bar is not set\n"; } // Set $foo->bar to 'foobar' $foo->bar = 'foobar'; // Print the value of $foo->bar echo $foo->bar, "\n"; // foobar // Check if $foo->bar ($foo->elem['bar']) is set if (isset($foo->bar)) { echo "\$bar is set\n"; } else { echo "\$bar is not set\n"; } ?> Now, since we access the properties of $foo in a 'virtual' manner - meaning $foo->bar doesn't really exist, it's actually $foo->elem['bar'] (if it were public, that is) - we can assume that we can check for property existance in the same 'virtual' way, right? Wrong. If we could, the above would output this: $bar is not set foobar $bar is set Yet it returns: $bar is not set foobar $bar is not set If we want to check whether or not $bar exists in $foo, we have to add a method to the Foo class: public function isSet ($prop) { if (isset($this->elem[$prop])) { return TRUE; } else { return FALSE; } } Which is rather dumb, considering that the intention of isset() is to check whether or not a variable exists! So far there has been two suggestions as to what can be done: 1. Change isset so that it automatically detects overloaded properties 2. Let the user define a custom __isSet() method, similar to the one above, that is called each time a property of the class is checked with isset() Maybe there's some other angles/ideas/suggestions? -- Daniel Schierbeck