Please explain this code...

[Sharif]

Can someone please explain this to me:

$uid = isset($_POST['uid']) ? $_POST['uid'] : $_SESSION['uid'];

I've never seen it before... what the heck is it doing?

[drawmack]

$uid = isset($_POST['uid']) ? $_POST['uid'] : $_SESSION['uid'];

if is a more compact version of

if(isset($_POST['uid']) {
    $uid = $_POST['uid'];
} else {
    $uid = $_SESSION['uid'];
}

[hessian]

If the value of the first subexpression is TRUE (non-zero), then the second subexpression is evaluated, and that is the result of the conditional expression. Otherwise, the third subexpression is evaluated, and that is the value.

http://us4.php.net/manual/en/language.expressions.php

[maxpup979]

it is a variation on the old if/then/else syntax.

I believe that it is much more common in c/c++