Preventing "undefined variable" notice

[bunner_bob]

I have a number of situations like the following:

foreach ($array as $value) {
    $concat .= $value;
}

echo $concat;

Of course when error checking in E_ALL mode, I get a notice of an undefined variable ($concat), because I'm starting right off by appending to it.

So I can either declare:
$concat = null;
or
$concat = '';

at the beginning of my loop. Which is the better choice?

Also, how do either of these options interact with isset()? Am I right in guessing the former will return false, and the latter true, or will they both return true?

Thanks

• Bob

[planetsim]

You could even set the variable to just true.

I dont think it matters much how you initiate the blank variable. However when its going to a string i usually just do this

$string = '';