从二维数组中查找时间的总和

你好，我要找到总和，但有类似Invalid argument supplied for foreach()的错误显示如何检查错误

我的代码是

我有这样的时间

$SQL = "SELECT o_duration FROM total WHERE location=('".$location_c[$k]."') AND sub_cat=('".$id."') AND dateid BETWEEN '".$trgD."' AND '".$date2."'";
$result = mysql_query($SQL);
$s="0";
$duration_c[$k]=array();
while ($db_field = mysql_fetch_array($result)) {
$duration_c[$k][$s]= $db_field['o_duration'];
$s++;
}

然后我用for循环将其打印在表格中

<?php
for($i=0;$i<$l;$i++)
{ 
?>
<td width="154" class="alt" align="center"><?php  echo sum_the_time($duration_c[$i])
?></td> <?php } ?>

function sum_the_time($times) {
  $seconds = 0;
  foreach ($times as $time1)
  { 
list($hour,$minute,$second) = explode(':', $time);
$seconds += $hour*3600;
$seconds += $minute*60;
$seconds += $second;
 }
 $hours = floor($seconds/3600);
 $seconds -= $hours*3600;
 $minutes  = floor($seconds/60);
 $seconds -= $minutes*60;
 // return "{$hours}:{$minutes}:{$seconds}";
 return sprintf('%02d:%02d:%02d', $hours, $minutes, $seconds);
 }