Additional thing - when you don't send any requests to Apache and MySQL for some time, sample script seems to work. But just for one request, when you press "Refresh" in your browser and run it second time, it gives output i've posted.

For calling stored procedures you have to use mysqli_multi_query.

Why I should use mysqli_multi_query()? Where is it documented, that I should use mysqli_multi_query() for stored procedures?

But the following code with mysqli_multi_query() doesn't work either:

-------
// $db is mysqli object
if ($db->multi_query('CALL test_proc(1); CALL test_proc(1);')) {
    if ($result = $db->store_result()) {
        $res = $result->fetch_assoc();
        print_r($res);
        $result->close();
    }
    else
        echo '<br />No result!<br />';
    $db->next_result();
    if ($result = $db->store_result()) {
        $res = $result->fetch_assoc();
        print_r($res);
        $result->close();
    }
    else
        echo '<br />No result<br />';
}
else
    echo '<br />'.$db->error.'<br />';
-----

Produces the following output:
-----
Array
(
    [id] => 1
    [txt] => test1
)

No result
-----

(Expected was two identical results)

When a stored procedure returns a resultset, MySQL returns at least two resultsets: first for the SELECT CALL inside the stored procedure. 2nd for the call of the stored procedure itself (2nd usually is only an OK or ERR packet)

mysqli_query fetches only one resultset, the second is still on socket: subsequent mysqli_ calls will fail, cause the sockets is still blocked.

Therefore you should use mysqli_next_result and mysqli_multi_query instead.

Ok, got the point. Additional $db->next_result() with $db->multi_query() was solution. My fault, sorry!