Basic isset() Question

jessjenn

Whenever I process variables from forms, I always use isset($_POST['whatever']) for checking the existence of it. This is just in case the user decides to go to that page directly without submitting the form. On top of that, if I want to check if the data is numeric, then I do

if(isset($POST['whatever']) && is_numeric($POST['whatever']))

My problem is that when I'm dealing with a bunch of form variables this checking can get quite long because I check for the datatype (is_numeric) and its existence (isset).

My question is, if I even have to use isset() when checking for datatypes. Would using functions like is_numeric or any "is" function be enough? Is adding isset() in my validation just a waste if I'm combining it with "is" functions?

Any help is appreciated. Thanks!

LordShryku

isset is usually the first check you should do. Newer versions of PHP throw a notice if you try to do something to a variable that isn't set. So fo the tightest, most versatile code possible, checking isset should always come first.

I know your pain though. My usual methos of checking for a set variable, and making sure it has a value would be

if(isset($blah) && !empty($blah)) {

After doing something like that so many times, it's just second nature anymore.

swr

Originally posted by LordShryku
if(isset($blah) && !empty($blah)) {

I'm pretty sure you can use just empty, and skip the isset. If $blah is not defined, empty will simply return true without raising a notice. Works for me with PHP 4.x and full error reporting.

I generally prefer to create a function to get form variables, that will handle the isset checks:

function getvar($var, $default = '') {
    if (!isset($_REQUEST[$var])) return $default;
    if (get_magic_quotes_gpc()) {
        return stripslashes($_REQUEST[$var]);
    }
    else {
        return $_REQUEST[$var];
    }
}

LordShryku

Yes, you could, but that was only an example. Also, doesn't hurt :p

jessjenn

Thanks for the suggestions guys! Guess I'm stuck with isset()!

Weedpacket

Depending on what you do when form variables are set/not set, you could store the names of all the variables you're checking for in an array, and then loop through that array:

foreach($form_variables as $form_variable)
{ if(!isset($_POST[$form_variable]))
{//...that one's not set
}}

philipolson

If you feel like it, and know why an E_NOTICE error will happen and just want to supress it, you can always use @ like so:

if (@is_numeric($foo)) {
    echo "$foo is numeric, so it must also be set.";
}

Don't blindly use @ though, and typically one will catch an error when using it, like so:

$result = @mysql_query($sql);
if (!$result) {
    echo "Houston we have a problem, it is: " . mysql_error();
    exit;
} else {
    echo "The query ($sql) ran perfectly!  So the Germans would have us believe.";
}

We supress the Warning and use our own "error handling". Anyway, I'm starting to get offtopic here 🙂