按日期排序foreach给出警告：usort（）期望参数1为数组，给定为null

问题描述：

I have a .php that retrieve fields from my Joomla database and then echo them with a foreach function:

<?php                   
  $jquery1 = "SELECT `fulltext`,alias,metakey,publish_up,metadesc FROM xxx_content  WHERE catid=22 AND state= '1'";
  $jdb1->setQuery( $jquery1 );
  $jfeed1= $jdb1->loadObjectList();
  foreach ($jfeed1 as $jitem1):
?>
<li>
 <div>
  <?php                                 
  $oldLocale = setlocale(LC_TIME, 'en_US');
  echo strftime("%a %d %b %Y", strtotime($jitem1->publish_up)); 
  setlocale(LC_TIME, $oldLocale);
  ?>
 </div>
 <div><?php echo $jitem1->fulltext; ?></div>
</li> 
<?php endforeach; ?>

However I would like to sort the foreach function by date, I have tried two different way of doing it (based on other SE questions) but each time I get this warning:

Warning: usort() expects parameter 1 to be array, null given in...

Here is my first try:

$jfeed1= $jdb1->loadObjectList();
function date_compare($a, $b)
{
   $t1 = strtotime($a['publish_up']);
   $t2 = strtotime($a['publish_up']);
   return $t1 - $t2;
}    
usort($jitem1, 'date_compare');
foreach ($jfeed1 as $jitem1):

And here was my second try:

$jfeed1= $jdb1->loadObjectList();
usort($jfeed1->publish_up, function($a, $b) {
$date1 = DateTime::createFromFormat('Y-m-d H:i:s', $a);
$date2 = DateTime::createFromFormat('Y-m-d H:i:s', $b);
return $date1 > $date2;
});
foreach ($jfeed1 as $jitem1):

I've "learned" php just by looking at codes and tuto, so I am missing a lot of fondamental notions that why I don't understand what I am supposed to do to solve this warning. Thanks for your help!

EDIT 1: The function

<?php
    var_dump($jfeed1)
?>

gives me for the first item:

array(22) { [0]=> object(stdClass)#318 (5) { ["fulltext"]=> string(212) "Yesterday ..." ["alias"]=> string(3) "237" ["metakey"]=> string(7) "Romania" ["publish_up"]=> string(19) "2011-11-15 09:06:39" }

EDIT 2

$jfeed1= $jdb1->loadObjectList();

function date_compare($a, $b)
{
   $t1 = strtotime($a['publish_up']);
   $t2 = strtotime($b['publish_up']);
   return $t1 - $t2;
}    
usort($jfeed1, 'date_compare');
foreach ($jfeed1 as $jitem1):

答

You can sort out each array entry by the date directly in the query with:

ORDER BY publish_up DESC (descending order)
ORDER BY publish_up ASC (ascending order)

As in:

$jquery1 = "SELECT `fulltext`,alias,metakey,publish_up,metadesc FROM xxx_content  WHERE catid=22 AND state= '1' ORDER BY publish_up ASC";

If you want to keep this PHP function date_compare then you have to replace:

$a['publish_up']

$a->publish_up

As in:

$jfeed1= $jdb1->loadObjectList();
function date_compare($a, $b)
{
   $t1 = strtotime($a->publish_up);
   $t2 = strtotime($b->publish_up);
   return $t1 - $t2;
}    
usort($jfeed1, 'date_compare');
foreach ($jfeed1 as $jitem1):

return $t1 - $t2; is ascending

return $t2 - $t1; is descending

按日期排序foreach给出警告：usort（）期望参数1为数组，给定为null

相关推荐