Using PHP 5.3 ?: operator

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"?

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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.

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Unfortunately you cannot use it for the purpose you'd like to use it for:

Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise.

So you'll still have to use isset or empty() - the ?: operator does not include an isset check. What you need to use is:

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

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Just for completeness, another way to achieve it is to pull operator rank:

 $page = (int)$_GET["page"]  or  $page = 1;

Many people perceive this as unreadable however, though it's shorter than isset() constructs.

Or if you are using input objects or any other utility class:

 $page = $_GET->int->default("page", 1);

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