class a {
function __get($property){...}
}
$obj = new a();
var_dump(isset($obj->newproperty));
Seems the answer is nope but why?
Because it checks __isset rather than retrieving it using __get.
It is a much better option to call __isset, as there is no standard on what is empty. Maybe in the context of the class null is an acceptable value. You could also have a class that if the member didn't exist, it returned a new empty object, which would break isset($myObj->item) as in that case it would always return true.
It just isn't; you can use __isset instead. This is laid out here.
No, __get should not be triggered when you're trying to determine whether a property is set : testing if a property is set is not the same thing as trying to get its value.
Using isset triggers the __isset magic method.
See :
isset- and Overloading
The magic function __get is only called when you try to access a property that doesn't exist. Checking whether a property exists is not the same as retrieving it.
Class A{
public function __get($key){
...
}
public function __set($key,$name){
...
}
public function __unset($key){
...
}
public function __isset($key){
...
}
}
$obj = new A();
$get = $obj->newproperty;//$obj->__get("newproperty")
$obj->newproperty = "X";//$obj->__set("newproperty","X")
$bool = isset($obj->newproperty);//$obj->__isset("newproperty")
unset($obj->newproperty);//$obj->__unset("newproperty")
来源：https://stackoverflow.com/questions/2306979/will-isset-trigger-get-and-why