<?php
    function getTasks()
    {
        $query = 'SELECT task_id, task FROM tasks ORDER BY rank';
        $result = mysql_query($query);
 
        $tasks = array();
        while ($row = mysql_fetch_object($result)) {
            $tasks[$row->task_id] = $row->task;
        }
 
        return $tasks;
    }

    function taskOrder($key)
    {
        if (!isset($_POST[$key]))
            return;
 
        $tasks = getTasks();
        $queries = array();
        $rank = 1;
 
        foreach ($_POST[$key] as $task_id) {
            if (!array_key_exists($task_id, $tasks))
                continue;
 
            $query = sprintf('UPDATE tasks SET rank = %d WHERE task_id = %d',
                             $rank,
                             $task_id);
 
            mysql_query($query);
            $rank++;
        }
    }
?>