How to check form input against PHP variable?

Question

I have a variable pulled from a WordPress meta array - $vCode.

This variable is a 5 digit number.

On the page front-end I have an HTML form requesting a code to be entered and a submit button.

Upon submit I want the entered code to be checked against $vCode and display either "success" or "fail" if it matches or not.

1. Should I be using an HTML form here or PHP?
2. What is the best way to run the check without leaving the page?

This is what I have so far:

$vCode = 11111;
$message = "";
if(!isset($_POST['submitbutton'])){
$message = "not submitted";
} elseif ((isset($_POST['submitbutton'])) && ($input = $vCode)) {//check if form was submitted
  $input = $_POST['vCode']; //get input text
  $message = "Success! You entered: ".$input;
  } elseif ((isset($_POST['submitbutton'])) && ($input != $vCode)) {
  $input = $_POST['vCode'];
  $message = "OOps";
}
?>
<form action="" method="post">
<?php echo $message; ?>
  Validation Code:<br>
  <input type="number" name="vCode" value=""><br>
  <input type="submit" name="submitbutton" value="Submit">
</form>

This is always showing that I entered the correct number?

Thanks as always.

Answer 1

Your problem is this bit:

$input = $vCode

That is not comparing the variables. It's assigning the value of $vCode to $input. If you want to compare the two values, you need to use == or ===.

$input == $vCode

It still wouldn't work though, because you haven't actually defined $input. You're only defining it after the comparison, which isn't much use.

So your logic needs to look like this:

$vCode   = 11111;
$message = '';

if( ! isset( $_POST['submitbutton'] ) ) {
    $message = 'not submitted';
} else {
    $input = $_POST['vCode'];

    if ( $input == $vCode ) {
        $message = 'Success! You entered: ' . $input;
    } elseif ( $input != $vCode ) {
        $message = 'OOps';
    }
}

Note that:

• We're assigning $_POST['vCode'] to $input before checking it.
• We're not bothering to check if $_POST['submitbutton'] is set, because the only reason that code would be running is if it was, because of the first condition.
• We're using == to compare the value. We're using == and not ===, because $vCode is an integer, while $_POST['vCode'] will be a string. If you're actually getting $vCode from post meta, then it will also be a string, in which case you can use ===.

Regarding that last point, the best solution would be to convert them both to integers and use a strict comparison:

if ( (int) $input === (int) $vCode ) {