PHP snippet to show how to handle multiple select, maintaining select options.

mulitple_select.php

<?php

// Initial value for demo
$DPRpriority = array(array('name' => "Crimes Against Persons", 'selected' => false),
		     array('name' => "Disturbances", 'selected' => false),
		     array('name' => "Assistance / Medical", 'selected' => false),
		     array('name' => "Crimes Against Property", 'selected' => false),
		     array('name' => "Accidents / Traffic Problems", 'selected' => false),
		     array('name' => "Suspicious Circumstances", 'selected' => false),
		     array('name' => "Morality / Drugs", 'selected' => false),
		     array('name' => "Miscellaneous Service", 'selected' => false),
		     array('name' =>"Alarms", 'selected' => false));

echo "<h1>Initial value of DPRpriority:</h1><ul>\n";
foreach ($DPRpriority as $item => $value) {
  echo "<li> ".$item.": ".$value['name']." selected: ".$value['selected']." </li>\n";
}
echo "</ul>\n";

if (count($_POST) > 0) { 
  // something was posted:
  echo "<h1>\$_POST:</h1><pre><code>\n";
  var_dump($_POST);
  echo "</code></pre>\n";

  echo "<h2>Items selected:</h2><ul>\n";
  foreach ($_POST['DPRType'] as $item) {
    $DPRpriority[$item]['selected'] = true;
    echo "<li>".$item.": ".$DPRpriority[$item]['name']."</li>\n";
  }
  echo "</ul>\n";

  echo "<h1>Final value of DPRpriority:</h1><ul>\n";
  foreach ($DPRpriority as $item => $value) {
    echo "<li> ".$item.": ".$value['name']." selected: ".$value['selected']." </li>\n";
  }
  echo "</ul>\n";
}

?>

<form method="post">

<select name="DPRType[]" id="DPRType[]" multiple onchange="" size="<?php echo count($DPRpriority) ?>">
  <?php foreach ($DPRpriority as $index => $value) { ?>
<option value="<?php echo $index; ?>"<?php if ($value['selected']) {echo ' selected="selected"';} ?>><?php echo $value['name'];?></option>
     <?php } ?>
</select>

<input type="submit" name="submit" value="submit" />

</form>