使用PHP 5.3？：运算符

Question

With this test page:

$page   = (int) $_GET['page'] ?: '1';
echo $page;

I don't understand the output I'm getting when page is undefined:

Request   Result
?page=2   2
?page=3   3
?page=    1
?         error: Undefined index page

Why the error message? It's PHP 5.3; why doesn't it echo "1"?

Answer 1

The proper way (in my opinion) would be:

$page = isset($_GET['page']) ? (int) $_GET['page'] : 1;

Even if you used the new style, you would have problems with ?page=0 (as 0 evaluated to false). "New" is not always better... you have to know when to use it.