Secure GET & POST Methods

common.php

<?php

class Common
{
    /*--------------------- $_GET & $_POST ----------------- START */

    /**
     * Get $_GET content, array or array item in filtered way
     *
     * @param object $parameter could be array or array item
     */
    public function get($parameter = null)
    {
        if ($parameter == null) {
            if (is_array($_GET)) {
                $request = array();

                foreach ($_GET as $key => $param) {
                    $request[$key] = strip_tags(trim(addslashes(htmlspecialchars($param))));
                }

                return $request;
            }
        } else if (isset($_GET[$parameter])) {
            return strip_tags(trim(addslashes(htmlspecialchars($_GET[$parameter]))));
        }

        return false;
    }

    /**
     * Get $_POST content, array or array item in filtered way
     *
     * @param object $parameter could be array or array item
     */
    public function post($parameter = null)
    {
        if ($parameter == null && $_POST) {
            if (is_array($_POST)) {
                $request = array();

                foreach ($_POST as $key => $param) {
                    $request[$key] = htmlspecialchars(addslashes(trim($param)));
                }

                return $request;
            }
        } else if (!empty($_POST[$parameter])) {
            if (is_array($_POST[$parameter])) {
                $request = array();

                foreach ($_POST[$parameter] as $param) {
                    $request[] = htmlspecialchars(addslashes(trim($param)));
                }

                return $request;
            }

            return htmlspecialchars(addslashes(trim($_POST[$parameter])));
        }

        return false;
    }

    /*--------------------- $_GET & $_POST ----------------- END */
}

usage.php

<?php

$common = new Common();

// returns $_GET array with all contains
$common->get();

// get single $_GET parameter value
$common->get('some_parameter');

// returns $_POST array with all contains
$common->post();

// get single $_POST parameter value
$common->post('some_parameter');