这个问题似乎已经应该在这里回答了，但是我找不到它，可能是由于缺乏术语。希望处于相同情况的其他人可以从中受益。
我有一个数组 $post_item。（下）例如，我从中打印数据
$post_item->ID
有没有办法按照我打印的顺序获取哪个项目。换句话说，我想数一数项目。
如果该项目是 ID 为 9 的项目，我想返回 0。如果是 ID 为 12 的那个，我想返回 1 等。
stdClass Object
(
[ID] => 9
[post_author] => 1
[post_date] => 2012-05-18 12:01:49
[post_date_gmt] => 2012-05-18 12:01:49
[post_content] =>
[post_title] => barnbildarkiv
[post_excerpt] =>
[post_status] => inherit
[comment_status] => open
[ping_status] => open
[post_password] =>
[post_name] => barnbildarkiv
[to_ping] =>
[pinged] =>
[post_modified] => 2012-05-18 12:01:49
[post_modified_gmt] => 2012-05-18 12:01:49
[post_content_filtered] =>
[post_parent] => 0
[guid] => http://dev.nuagency.se/wp-content/uploads/2012/05/barnbildarkiv.jpg
[menu_order] => 0
[post_type] => attachment
[post_mime_type] => image/jpeg
[comment_count] => 0
[filter] => raw
)
stdClass Object
(
[ID] => 12
[post_author] => 1
[post_date] => 2012-05-18 12:02:00
[post_date_gmt] => 2012-05-18 12:02:00
[post_content] =>
[post_title] => animals_hm_giftcards
[post_excerpt] =>
[post_status] => inherit
[comment_status] => open
[ping_status] => open
[post_password] =>
[post_name] => animals_hm_giftcards
[to_ping] =>
[pinged] =>
[post_modified] => 2012-05-18 12:02:00
[post_modified_gmt] => 2012-05-18 12:02:00
[post_content_filtered] =>
[post_parent] => 0
[guid] => http://dev.nuagency.se/wp-content/uploads/2012/05/animals_hm_giftcards.jpg
[menu_order] => 0
[post_type] => attachment
[post_mime_type] => image/jpeg
[comment_count] => 0
[filter] => raw
)
stdClass Object
(
[ID] => 63
[post_author] => 1
[post_date] => 2012-05-21 09:27:41
[post_date_gmt] => 2012-05-21 09:27:41
[post_content] =>
[post_title] => wren-2
[post_excerpt] =>
[post_status] => inherit
[comment_status] => open
[ping_status] => open
[post_password] =>
[post_name] => wren-2
[to_ping] =>
[pinged] =>
[post_modified] => 2012-05-21 09:27:41
[post_modified_gmt] => 2012-05-21 09:27:41
[post_content_filtered] =>
[post_parent] => 62
[guid] => http://dev.nuagency.se/wp-content/uploads/2012/05/wren-2.gif
[menu_order] => 0
[post_type] => attachment
[post_mime_type] => image/gif
[comment_count] => 0
[filter] => raw
)
如果需要"键"（0，1，2..）
$arr = array();
foreach($objects as $key=>$val) { $arr[$key] = $val; }
foreach($arr as $key=>$val) {
if ($val["ID"] == 9) { /* $key is 0,1,2.. */ }
}
也许对这个问题的更好解释可能会有所帮助。