advanced patterns when using PHP's `filter_input` with custom scenarios handling
I'm wondering if anyone has experience with I've searched everywhere and can't find a clear answer. I'm experiencing issues with `filter_input` in PHP 8.1 when trying to apply a custom behavior handling mechanism. I have set up a form that submits user input via POST, and I want to validate the input using `FILTER_SANITIZE_STRING`. However, I'm also using a custom behavior handler to capture and log any invalid inputs. The question arises when `filter_input` returns `null` instead of `false`, which makes it difficult to trigger my behavior handler. Here's the relevant part of my code: ```php // Custom behavior handler set_error_handler(function($errno, $errstr) { error_log("behavior[$errno]: $errstr"); }); // Processing the form input $name = filter_input(INPUT_POST, 'name', FILTER_SANITIZE_STRING); if ($name === null) { trigger_error('Input is invalid or not provided', E_USER_WARNING); } elseif ($name === false) { trigger_error('String filtering failed', E_USER_WARNING); } else { // Proceed with processing the valid input echo "Hello, " . htmlspecialchars($name); } ``` I expected `filter_input` to return `false` for invalid inputs or `null` if the variable isn't set, but I'm not seeing that behavior. Instead, when I submit an empty value, `$name` is `null`, which leads to my custom behavior handler being triggered. This seems to contradict the expected filtering behavior, and I need to figure out how to handle this correctly. I've also tried checking if the `name` key exists in `$_POST` before the `filter_input` call, but that doesn't seem to resolve the underlying scenario. Am I missing something in how `filter_input` works, or is there a better way to handle this scenario without losing the behavior feedback? Any insights would be appreciated! This is part of a larger web app I'm building.