!is_null() not working as expected

Question

dispatch_address_postcode

isn't mandatory and it will still run even if it's blank:

if (!is_null($_POST['personal_info_first_name']) && 
    !is_null($_POST['personal_info_surname']) && 
    !is_null($_POST['personal_info_email']) && 
    !is_null($_POST['personal_info_telephone']) && 
    !is_null($_POST['dispatch_address_country']) && 
    !is_null($_POST['dispatch_address_first_name']) &&
    !is_null($_POST['dispatch_address_surname']) && 
    !is_null($_POST['dispatch_address_address']) && 
    !is_null($_POST['dispatch_address_town']) && 
    !is_null($_POST['dispatch_address_postcode']) && 
    !is_null($_POST['dispatch_address_county']) && 
    (   ($_POST['payment_method'] == "Pay by credit card.") ||
        (
            ($_POST['payment_method'] == "Pay by new credit card.") && 
            !is_null($_POST['card_number']) && 
            !is_null($_POST['expiration_date']) && 
            !is_null($_POST['security_code'])
        )
    )
)

What gives?

Answer 1

"dispatch_address_postcode isn't mandatory and it will still run even if it's blank…"

Just look at that sentence again. If the field is not mandatory, it is perfectly okay if the code runs if the field is blank. If a field isn't mandatory, don't test it as mandatory.

The real problem is though, is_null only tests if the variable is null. POSTed values will never be null, if they're empty they will be '' (an empty string). All your !is_null tests will always be true, and you will get a warning if the variable isn't set (something you don't want to happen). The more appropriate test would be !empty.

Even more appropriate tests would include a test if the value appears to be valid (does email look like an email address, does telephone have at least x digits in it?). You should also loop through the fields to make your code more readable, endless nested and chained if conditions are no joy to look at.

$mandatoryFields = array('foo' => 'email', 'bar' => 'telephone');

foreach ($mandatoryFields as $field => $rule) {
    if (empty($_POST[$field]) || !validateByRule($_POST[$field], $rule)) {
        raiseHell();
    }
}

Answer 2

It looks like you're trying to make sure all post variables are submitted. Would you like help with that?

Using !empty() may not be the answer to your specific question, but it would definitely help with what it looks like you're trying to do.

empty() returns TRUE if the $_POST key isn't set, if its an empty array, or even if its an empty string, so using !empty() is a good way to make sure that the user has filled in the information.