How to use isset function in php properly?

What is the difference and which is better?

This one:

 if(isset($_POST['name'])){

 }

or this one:

 $name = $_POST['name'];
 if(isset($name)){

 }

I wanna know if there are differences between the two codes, and which is more efficient to use. Thank you in advance!

Solution

Hi The first one is right

if(isset($_POST['name'])){

 }

This will check $_POST['name'] is set or not.

but

$name = $_POST['name'];
 if(isset($name)){

 }

this will check $name is set or not. and it will go inside if because whether $_POST['name'] has value or not you have declared $name. So this will give wrong result