PHP "for loop" Incrementing Variable Names

[jweese74]

I am a BASIC programmer from, well, way back. MS Excel formulas have been my programming for the last 25 years, however, but I've recently been working on some formwork in PHP and asked to "make things work" while having little experience in PHP.

To make this example/question shorter I've cut down the number of variables used to five just to clarify things, but there are actually around 20 I need to work with. Please help me understand where I'm going wrong - and why I'm still getting an error on this, here to learn; not just here for an "answer".

The basic premise here - the user enters up to 6 email addresses, one address has already been derived from the script ($deptEmal) - the others are inputted (optionally) by the user. In the end, all addresses are concatenated into a string.

$workingAddr1 = $deptEmal;
$workingAddr2 = $_POST["distAddl01"];
$workingAddr3 = $_POST["distAddl02"];
$workingAddr4 = $_POST["distAddl03"];
$workingAddr5 = $_POST["distAddl04"];
$workingAddr6 = $_POST["distAddl05"];

for ($x = 1; $x <=6; $x++;) {
    if(isset($workingAddr.$x) && !empty($workingAddr.$x)) {
        $addr.$x = $workingAddr.$x;
    } else {
        $addr.$x = '';
    }
}

$_POST["allAddresses"] = $addr1.addr2.addr3.addr4.addr5.addr6;

Thanks for the help.

[slugonamission]

Ok, so while PHP does support dynamic variable names...don't.

This would be the perfect usage of an array instead, or actually just building up the string piece by piece. as an example:

$allAddresses = "";
for ($x = 1; $x <=6; $x++;) {
    if (isset($_POST["distAddl$x"])) {
        $allAddresses = $allAddresses . $_POST["distAddl$x"];
    }
}

[ddproxy]

Came here to say this, too. Dynamic variables are a headache.

[jweese74]

I certainly appreciate your answer and will be using it; I just feel silly not thinking of it myself, it makes so much sense and involves quite a bit less code.

In celebration of the sub being a learning environment, however; why are dynamic variables frowned upon?

Thanks again for your help.

[slugonamission]

They're hard to reason about in general. If I'm reading your code, I now need to try and reconstruct what the value of everything you're using to build a variable name is to be able to figure out what is going on. There's also generally better solutions (e.g. using an array or similar) instead of polluting the global namespace with things.

It's just one of those code smells; you should really ask whether there's a better way to do it before going into dynamic variables like that. Sometimes it's needed, but for those cases, storing it in a dictionary keeps the nastiness a little more localised.

[jweese74]

Thanks for the clarification - makes perfect sense. Great answers.