Знатокам php - Общие вопросы веб разработки

<?php
$db =& JFactory::getDBO();
$query = "SELECT * FROM #__users" ;
$db->setQuery($query);
$rows = $db->loadObjectList();
foreach ($rows as $row) {
 echo $row->id;
}
?>

<?php
$db =& JFactory::getDBO();
$query = "SELECT * FROM #__users" ;
$db->setQuery($query);
$rows = $db->loadObjectList();
$sum=0;
foreach ($rows as $row) {
 $sum+=$row->id;
}
echo $sum;
?>

<?php
$db =& JFactory::getDBO();
$query = "SELECT * FROM #__users" ;
$db->setQuery($query);
$rows = $db->loadObjectList();
if($rows)
    $sum = array_sum(array_map(function($el){return (int)$el->id;}, $rows));
echo $sum;
?>

$db = JFactory::getDBO();
$query = "SELECT COUNT(*) FROM #__users" ;
$db->setQuery($query);
$result = $db->loadResult();
echo $result;

$db = JFactory::getDBO();
$query = "SELECT SUM(id) FROM #__users" ;
$db->setQuery($query);
$result = $db->loadResult();
echo $result;