delete multiple registers of MySql DB

[pavmoxo]

I have this part of a form

<select name="actas2[]" size="5" multiple>
                <?
                    $sql = "select * from actas2 where area_ID = 1 order by year desc, number desc";
                    $query = query($sql);
                    $conta = mysql_num_rows($query);
                    for ($i=0;$i<$conta;$i++)
                    {
                        $arr = mysql_fetch_array($query);
                        ?>
                  <option value="<? echo $arr["acta_ID"]; ?>"><? echo trata_data1($arr["dia"])." -> acta ".$arr["number"]." realizada em ".$arr["day"]." de ".trata_month($arr["month"])." de ".$arr["year"]; ?><? if ($arr['active'] == 'n') { ?> - Inactivo<? }?></option>
                        <?
                    }
                ?>
                
                  </select>

And the php:

/* APAGAR */
    if(isset($_POST['apagar']))
    {
        if(!isset($_POST['actas2'])){ 
        $err = 'Não escolheu um registo!'; 
            } 
            else{ 
                if(is_array($_POST['actas2'])){ 
                    $id = implode(',',$_POST['actas2']); 
                } 
                else{ 
                    $id = $_POST['actas2']; 
                } 
                $sql = "delete from actas2 where actas2_ID in (" . $id . ") and area_ID = 1"; 
                $query = query($sql);
                    if ($query == 1)
                    {
                        echo "<script>alert('O documento foi apagada com sucesso.');</script>";
                    }
                    else
                    {
                        echo "<script>alert('Problemas ao remover o documento.');</script>";
                    }                
            } 
        
    } 

I don´t obtain the result that I want - delete one or more registries

[Atolar]

Why are you using query($sql) and not mysql_query($sql) ?