Question

I am building a page which allows our members to select their notification preferences based on a number of options. For example sake, I am giving the option for the member to select notifications when a new message arrives and when an update has occured. They can receive the notification via email, sms, both, or neither.

If I simply build it out as a number of:

HTML code

<tr>
    <td>Alert me when a new message comes in:</td>
</tr>
<tr>
    <td>
       <label><input name="ENREME" type="radio" style="margin-left:30px;" value="EMAIL" <?php if ($smscode == "7" || $smscode == "4") { ?>checked="checked"<?php } ?> tabindex="15" />Email</label>
       <label><input name="ENREME" type="radio" style="margin-left:30px;"  value="SMS" <?php if ($smscode == "7" || $smscode == "5") { ?>checked="checked"<?php } ?> />SMS</label>
       <label><input name="ENREME" type="radio" style="margin-left:30px;"  value="BOTH" <?php if ($smscode == "7" || $smscode == "6") { ?>checked="checked"<?php } ?> tabindex="15" />Both</label>
       <label><input name="ENREME" type="radio" style="margin-left:30px;" value="NONE" <?php if ($smscode == "0") { ?>checked="checked"<?php } ?> />Don't notify me</label>
    </td>
</tr>
<tr>
    <td>Alert me when a new update to my site occurs:</td>
</tr>
<tr>
    <td>
       <label><input name="RECRUITEME" type="radio" style="margin-left:30px;" value="EMAIL" <?php if ($smscode == "7" || $smscode == "1") { ?>checked="checked"<?php } ?> tabindex="15" />Email</label>
       <label><input name="RECRUITEME" type="radio" style="margin-left:30px;"  value="SMS" <?php if ($smscode == "7" || $smscode == "2") { ?>checked="checked"<?php } ?> /> SMS</label>
       <label><input name="RECRUITEME" type="radio" style="margin-left:30px;"  value="BOTH" <?php if ($smscode == "7" || $smscode == "3") { ?>checked="checked"<?php } ?> tabindex="15" />Both</label>
       <label><input name="RECRUITEME" type="radio" style="margin-left:30px;" value="NONE" <?php if ($smscode == "0") { ?>checked="checked"<?php } ?> />Don't notify me</label>
    </td>
</tr>

Variable Encoding and Storage

<?php
    if ($_POST['ENREME'] == "BOTH" && $_POST['RECRUITEME'] == "BOTH") {
        $notif = 15;
    } elseif ($_POST['ENREME'] == "BOTH" && $_POST['RECRUITEME'] == "SMS") {
        $notif = 14;
    } elseif ($_POST['ENREME'] == "BOTH" && $_POST['RECRUITEME'] == "EMAIL") {
        $notif = 13;
    } elseif ($_POST['ENREME'] == "BOTH" && $_POST['RECRUITEME'] == "NONE") {
        $notif = 12;
    } elseif ($_POST['ENREME'] == "EMAIL" && $_POST['RECRUITEME'] == "BOTH") {
        $notif = 11;
    } elseif ($_POST['ENREME'] == "EMAIL" && $_POST['RECRUITEME'] == "SMS") {
        $notif = 10;
    } elseif ($_POST['ENREME'] == "EMAIL" && $_POST['RECRUITEME'] == "EMAIL") {
        $notif = 9;
    } elseif ($_POST['ENREME'] == "EMAIL" && $_POST['RECRUITEME'] == "NONE") {
        $notif = 8;
    } elseif ($_POST['ENREME'] == "SMS" && $_POST['RECRUITEME'] == "BOTH") {
        $notif = 7;
    } elseif ($_POST['ENREME'] == "SMS" && $_POST['RECRUITEME'] == "SMS") {
        $notif = 6;
    } elseif ($_POST['ENREME'] == "SMS" && $_POST['RECRUITEME'] == "EMAIL") {
        $notif = 5;
    } elseif ($_POST['ENREME'] == "SMS" && $_POST['RECRUITEME'] == "NONE") {
        $notif = 4;
    } elseif ($_POST['ENREME'] == "NONE" && $_POST['RECRUITEME'] == "BOTH") {
        $notif = 3;
    } elseif ($_POST['ENREME'] == "NONE" && $_POST['RECRUITEME'] == "SMS") {
        $notif = 2;
    } elseif ($_POST['ENREME'] == "NONE" && $_POST['RECRUITEME'] == "EMAIL") {
        $notif = 1;
    } elseif ($_POST['ENREME'] == "NONE" && $_POST['RECRUITEME'] == "NONE") {
        $notif = 0;
    }
?>

I am left to code for 16 possible variables (and thus creating over 100 lines of code). Can anybody think of a better way to consolidate this code? Based on the selections made, I want the result to equal a single digit (i.e. 28 equals, send email and SMS notifications for both new messages and updates).

Creating a new table or database and making reference calls is not a solution so please do not suggest that.

Thank you!

Answer 1

It sounds like what you’re really looking for is a bitwise solution. Using bits, you’re able to store a lot of boolean switches into a single integer. This answer uses some roundabouts to keep things clear – you could use the int values directly instead of the pow(2,X) shown below… consider it “teaching a man to fish”.

If you’d like a more succint, though complex to understand solution, take a look at Ast Derek’s answer. They both do the same thing and operate on the same principle.

In order to store these, let’s do two simple switches:

switch($_GET['x']) {
   case 'Email': $x = pow(2,0); break; // 1
   case 'Sms':   $x = pow(2,1); break; // 2
   case 'Both':  $x = pow(2,0) + pow(2,1); break;// 3
   default: $x = 0;
}

switch($_GET['y']) {
   case 'Email': $y = pow(2,2); echo "Y Email"; break; // 4
   case 'Sms':   $y = pow(2,3); echo "Y SMS"; break; // 8
   case 'Both':  $y = pow(2,2) + pow(2,3); echo "Y Both"; break; // 12
   default: $y = 0;
}

As you can see, the None options are absent. None is simply the absence of a either Email or SMS. Also, the Both option is defined not as a separate option, but as a combination of both.

Now that we have these value, we can combine these two numbers into a single number, since their relevant bits are both in different ranges.

$z = $x | $y;

What happens when looking at the bits is the following – assume that we’ve got X = Email, and Y = Both.

x = 0001 -> (0 + 0 + 0 + 1) -> 1
y = 1100 -> (8 + 4 + 0 + 0) -> 12
    -----
OR: 1101 -> (8 + 4 + 0 + 1) -> 13

What this will give you is the following possible results:

0: x = none, y = none
1: x = email, y = none
2: x = sms, y = none
3: x = both, y = none
4: x = none, y = email
5: x = email, y = email
6: x = sms, y = email
7: x = both, y = email
8: x = none, y = sms
9: x = email, y = sms
10: x = sms, y = sms
11: x = both, y = sms
12: x = none, y = both
13: x = email, y = both
14: x = sms, y = both
15: x = both, y = both

To detect which have chosen, simply reverse the operation.

So you can test things, I’ve put the whole setup in a Github Gist for you to enjoy and tinker with: http://gist.github.com/505272

Feel free to ask if you need clarification; I’m not sure I explained it very clearly :/