reference appendices

Available Filters

The Filter extension provides validation and sanitisation filters. Validation asks whether input satisfies a format; sanitisation transforms input and must not be mistaken for domain validation or output escaping.

Use This Reference When

Validating email addresses and integers at input boundaries.
Inspecting available filters with filter_list().
Separating input checks from HTML escaping and business rules.

Validate an Integer

PHP example

<?php

$value = filter_var('12', FILTER_VALIDATE_INT, [
    'options' => ['min_range' => 1],
]);
var_dump($value);

// Prints:
// int(12)

Do not use sanitisation as a security blanket. Validate expected input, model the domain rule, and escape output for its destination.

Practice

Validate a Port Number

Use filter_var() to validate an integer port between 1 and 65535. Test a valid and invalid value.

Show solution

Use FILTER_VALIDATE_INT with min_range and max_range options. Compare the result strictly against false because zero can be a valid integer in other domains.