php ternary shorthand for use in template

Question

I'm building my first application with Kohana, and using a basic templating system within that. In my templates I want to echo variables for the various contents of the page, but only if each variable is set, and I want to keep the code in the templates as short as possible, so something like this:

<?=$foo?>

works fine if the variable is set, but if it's not I get a notice. So I thought a ternary operator would do the trick nicely:

<?=$foo?:''?>

according to the PHP manual, from 5.3 it's ok to leave out the middle part and the above should output nothing if the variable isn't set, but I still get an error notice."Notice: Undefined variable: foo in /"

I can get the desired result with a slight alteration to suppress the notice:

<?=@$foo?:''?>

but I know that's generally not beset practice and would like a better solution if possible, while still keeping the code to a minimum in the template files.

the following works, but it's not as concise (mainly because my actual variables can be quite long):

<?=isset($foo)?$foo:'';?>

am I missing something or doing something wrong?

Answer 1

The ternary operation is not meant to replace checking with isset() - it needs it's variable defined or else you get a notice.

Template engines usually offer a way to use a default value instead, but they also do not use pure PHP code. You you are out of luck here: Either suppress the notice, or use the longer code variant. Or ensure that every variable is set, which enables you to consider any notice an error.

Answer 2

To avoid notices for undefined variables, you can create custom function that takes first parameter by reference

function tplvar(&$value, $default = '') {
    return ($value !== null) ? $value : $default;
}

<?=tplvar($foo, 'bar');?>

Uninitialized variables passed by reference will be seen as nulls.