Input Filter

filter.php

<?php

// This class I used several times before:
// @see https://gist.github.com/jm42/e7e788d7e257ce1f93c7
// @see https://gist.github.com/jm42/4fc873e91b3835ade45f

class InputFilter implements \ArrayAccess {
    private $input;
    private $cache = [];

    public function __construct($input) {
        $this->input = $input;
    }

    public function offsetExists($offset) {
        if (array_key_exists($offset, $this->cache)) {
            return true;
        }
        return filter_has_var($this->input, $offset);
    }

    public function offsetGet($offset) {
        if (array_key_exists($offset, $this->cache)) {
            return $this->cache[$offset];
        }
        return $this->cache[$offset] = filter_input($this->input, $offset);
    }

    public function offsetSet($offset, $value) {
        $this->cache[$offset] = $value;
    }

    public function offsetUnset($offset) {
        unset($this->cache[$offset]);
    }
}