PHP使用三元运算符的未定义索引

Question

my PHP version is 5.3.5.

The code:

$num = $_REQUEST['num'] ?: 7;

The error:

Notice: Undefined index: num in C:\path\to\file.php on line 34

Any suggestions?

Answer 1

$num = isset($_REQUEST['num']) ? $_REQUEST['num'] : 7;

我假设你想要$_REQUEST['num'] ，否则设置为7。

Answer 2

Isn't using error suppression for short assignment code good ?.

we can write $price = @$rec['Product']['new'] ?: $rec['Product']['old'];

Using @ saved me from repeating of same variable and allowed me to use short cut ternary operator without generating notice.

I know using @ is considered not good but for this particular case, I don't imagine anything could go wrong ever.

Thanks.

Answer 3

This is expected behavior; according to http://bugs.php.net/bug.php?id=45760 , the ?: shortcut is just that: a shortcut.

In other words:

$num = $_REQUEST['num'] ?: 7;

is evaluated identically to:

$num = $_REQUEST['num'] ? $_REQUEST['num'] : 7;

and everything that implies (and is addressed quite adequately by the other answers in the thread).

Answer 4

If it isn't in the request, you may get a warning.

You're better off doing this:

$num = (array_key_exists('num', $_REQUEST)) ? intval($_REQUEST['num']) : 7;

Answer 5

I second dhaval solution of using @ error suppression, what is more readable:

$num = @$_REQUEST['num'] ?: 7;

..or..

$num = (array_key_exists('num', $_REQUEST)) ? $_REQUEST['num'] : 7;

I know which I would prefer to read if I was trying to understand someone else's code. I think it provides the happy medium between setting error_reporting to E_ALL & ~E_NOTICE (very bad) and the boilerplate code above.

Answer 6

$num = (isset($_REQUEST['num'])) ? $_REQUEST['num'] : 7;

Answer 7

Accessing an array with an index that doesn't exist is always going to throw a notice. You need to either ignore the notice since that does return null, or technically you're supposed to use array_key_exists .