What is the simplest way to do this if statements in php?

I have this form

<form class="account-form" method="post">

<input type="radio" name="all"  />All<br />
<input type="radio" name="part"  />Part<br />
<label>How many channels to export?</label><br />
<input type="number" name="part" value="" /><br />
<label>Select user</label><br />
<input type="test" name="user" value="" /><br />
<label>Execlude user</label><br />
<input type="test" name="exuser" value="" /><br />

<label>Select numbers region</label><br />
<input type="checkbox" name="uk" value="uk" />Export UK<br />
<input type="checkbox" name="us" value="us" />Export US <br />
<button type="submit" name="submit" value="submit" />Submit <br />

</form>

and I want to export some data form my db according to the choices in the form so far I'm doing it like this

if (isset($_POST)){
if (isset($_POST[all])){
$file = '../files/'.$notsoldcount." All.txt";
$fp=fopen($file,"w");
    while($row = mysql_fetch_array($notsold, MYSQL_ASSOC))
    {
        $phone = $row['phone'] ;
        $pass = $row['password'] ;
        $id = $row['identity'] ;
        $data = $phone.",".$pass.",".$id.","."\r\n";
        fwrite($fp,$data);
        mysql_query("UPDATE `datask` SET `sold`= 1 WHERE phone = '$phone'");
    }
    fclose($fp);

    echo '
            <div class="alert alert-warning alert-dismissible" role="alert">
                <strong>Okey!</strong> Your file is ready for <a download href="'.$file.'">Download</a>
            </div>
        ';  
}
else {

    if (isset($_POST[part]) && ($_POST[uk])){
    $some = $_POST[some];
    // Same here
}

else if (isset($_POST[some]) && ($_POST[us])){
    // same here 

}
else if (isset($_POST[some] && ($_POST[user])){
    //same


}
    and so on for all choices 
}
}

I need to export data according the choices but there are a lot of odds like

• all data


• all data excluding 1 user


• all data for 1 user


• part of the data :


• part for all users


• part for all users excluding 1 user


• part for all users for us numbers


• part for all users for uk numbers


• part for 1 user for us numbers only


• part for 1 user for uk numbers only

using if, else if statements will result in a very long code, is there any way to shorten it?