Question

First off, I know the title is generic and not fitting. I just couldn’t think of a title that could describe my problem.

I have a table Recipients in MySQL structured like this:

id   |   email   |   status
1      foo@bar         S
2      bar@baz         S
3      abc@def         R
4      sta@cko         B

I need to convert the data into the following XML, depending on the status field. For example:

<Recipients>
    <RecipientsSent>
        <!-- Have the 'S' status -->
        <recipient>foo@bar</recipient>
        <recipient>bar@baz</recipient>
    </RecipientsSent>

    <RecipientsRegexError>
        <recipient>abc@def</recipient>
    </RecipientsRegexError>

    <RecipientsBlocked>
        <recipient>sta@cko</recipient>
    </RecipientsBlocked>
</Recipients>

I have this PHP code to implement this ($recipients contains an associative array of the db table):

<Recipients>

<RecipientsSent>
<?php
foreach ($recipients as $recipient):
    if ($recipient['status'] == 'S'):
        echo "<recipient>" . $recipient['email'] . "</recipient>";
    endif;
endforeach;
?>
</RecipientsSent>

<RecipientsRegexError>
<?php
foreach ($recipients as $recipient):
    if ($recipient['status'] == 'R'):
        echo "<recipient>" . $recipient['email'] . "</recipient>";
    endif;
endforeach;
?>
</RecipientsRegexError>
<?php /** same loop for the B status */ ?>

</Recipients>

So, this means that if I have 1000 entries in the table and 4 different status’ that can be checked, it means that there will be 4 loops, each one executing 1000 times.

How can this be done in a more efficient manner? I thought about fetching four different sets from the database, meaning 4 different queries, would that be more efficient? I’m thinking it could be done with one loop but but I can’t come up with a solution.

Any way this could be done with only one loop?

Answer 1

With one loop you can do following

<?php

$string1, $string2 = '';

foreach ($recipients as $recipient) {
  $recipient_email = "<recipient>" . $recipient['email'] . "</recipient>";

  switch($recipient['status']) {
    case 'a':
      $string1 .= $recipient_email;
      break;
    case 'b':
      $string2 .= $recipient_email;
      break;
  }
}
?>

<Recipients>
  <RecipientsSent>
    <?php echo $string1; ?>
  </RecipientsSent>
  <RecipientsRegexError>
    <?php echo $string2; ?>
  </RecipientsRegexError>
</Recipients>