如何使用strtotime转换日期并在foreach中排序[重复]

function getSubMenu($page){
  $children=getChildren($page);

  // sorting by date
  usort($children, 'date_compare');

  $sliced = array_slice($children , 0, 10);

  foreach ($sliced as $subpage){
    $title=returnPageField($subpage,'title');
    $date=returnPageField($subpage,'pubDate');
    $url=returnPageField($subpage,'slug');
    echo '<li><a href="/'.$url.'.html">'.$title.'</a>'.$date.'</li>';
  }
} 

function date_compare($a, $b)
{
    $t1 = strtotime($a['pubDate']);
    $t2 = strtotime($b['pubDate']);
    return $t1 - $t2;
}