Untitled

<?php
session_start();

if (!isset($_SESSION['errors'])) {
    $_SESSION['errors'] = array();
}

if (isset($_REQUEST['action'])) {
    $_SESSION['errors'][] = 'Ошибка!!';
    header('Location: ?');
    exit();
}

?>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>
        <form action="?action=test" method="POST">
            <input type="text" value="12"/><input type="submit" value="hello"/>
        </form>
        <?php
        echo('<p>+'.count($_SESSION['errors']));
        if (count($_SESSION['errors']) != 0) {
            echo('<p>-'.count($_SESSION['errors']));
            $_SESSION['errors'] = array();
        }
        ?>
    </body>
</html>