What is the difference between isset() and __isset()?

Question

I need to know about magic function __isset() and normal function isset(). Actually what is the real difference between php language construct

Answer 1

Magic functions are automatically invoked (triggered) when something happens. Normal functions have to be specifically invoked by your php code.

In your case: __isset() will be automatically invoked when you have an isset() which is trying to get a non-accessible property.

Example:

root@folgore:/tmp/php# cat a.php 
att1);

// __isset will not be triggered:
isset($obj->att2);

root@folgore:/tmp/php# php a.php 
__isset invoked for att1