从下拉菜单选择更改下拉菜单的内容

我有一些下拉菜单。如果我选择其中一个，我想用与我所选择的内容可靠的东西来改变另一个的内容。我该怎么做呢?使用html和php。

例如，我有一个表

Year   with  id_year  and  year          
Stuff  with  id_stuf  and  stuff

如果我在第一个下拉菜单中选择了年份，那么在另一个下拉菜单中将只显示该年份的内容。

这是我的内容与下拉菜单

<div class="view">
    <form name="tabel" method="post" action="insertexamen.php">
    <table>
            <tr>
                <td>Data</td>
                <td><input type="date" name="data" value="data" required="required"/><br></td>
            </tr>
            <tr>
                <td>An</td>
                <td>
                    <?php
                        $sql_year="SELECT * FROM an";
                        $rez_year = mysqli_query($link,$sql_year);
                        echo "<select name='"year'" >";
                            while($year=mysqli_fetch_array($rez_year))
                            {
                                echo "<option value='"".$year['id_an']."'">".$year['grupa']."</option>";
                            }
                        echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td>Materie</td>
                <td>
                    <?php
                        $sql_mat="SELECT * FROM materii";
                        $rez_mat = mysqli_query($link,$sql_mat);
                        echo "<select name='"mat'" >";
                        while($mat=mysqli_fetch_array($rez_mat))
                        {
                            echo "<option value='"".$mat['id_mat']."'">".$mat['numemat']."</option>";
                        }
                            echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td>Profesor</td>
                <td>
                    <?php
                        $sql_proff="SELECT * FROM profesor";
                        $rez_proff = mysqli_query($link,$sql_proff);
                        echo "<select name='"proff'" >";
                        while($proff=mysqli_fetch_array($rez_proff))
                        {
                            echo "<option value='"".$proff['id_prof']."'">".$proff['numep']." ".$proff['prenumep']."</option>";
                        }
                            echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td>Asistent</td>
                <td>
                    <?php
                        $sql_profff="SELECT * FROM profesor";
                        $rez_profff = mysqli_query($link,$sql_profff);
                        echo "<select name='"profff'" >";
                        while($profff=mysqli_fetch_array($rez_profff))
                        {
                            echo "<option value='"".$profff['id_prof']."'">".$profff['numep']." ".$profff['prenumep']."</option>";
                        }
                            echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td>Sala</td>
                <td>
                    <?php
                        $sql_room="SELECT * FROM sala";
                        $rez_room= mysqli_query($link,$sql_room);
                        echo "<select name='"room'" >";
                        while($room=mysqli_fetch_array($rez_room))
                        {
                            echo "<option value='"".$room['id_s']."'">".$room['salaa']."</option>";
                        }
                            echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td>Tip</td>
                <td>
                    <?php
                        $sql_type="SELECT * FROM examen";
                        $rez_type= mysqli_query($link,$sql_type);
                        echo "<select name='"type'" >";
                        while($type=mysqli_fetch_array($rez_type))
                        {
                        echo "<option value='"".$type['id_tip']."'">".$type['tip']."</option>";
                        }
                        echo "</select>";
                    ?><br>
                </td>
            </tr>
            <tr>
                <td><input name="submit" type="submit" value="Trimite"/></td>
                <td><input name="reset" type="reset" value="Reset"/></td>
            </tr>   
</table>