PHP数组在foreach语句 - 范围问题中消失了吗？

Question

So, I have this very weird error - Some advanced PHP devs might also be considered somewhat weird.

In the 2nd foreach statement I have an array "$reply_each" created in that foreach statement and it is supposed to be "array_push()"-ed into another array called "$recent_discussion_each['discussion_replies_array']". This works while in the 2nd foreach statement. But as soon as the 2nd foreach statement finishes, the "$reply_each" array just vanishes - as if it was out of scope. Just to be sure it wasn't a scope issue, I initialized $reply_each at the beginning of the function but that didn't help - it must be something else.

Help, please?

Update: I probably should add that when I do a count() on $recent_discussion_each['discussion_replies_array'] inside the 2nd foreach statement, I get the correct value of 1. But when I do an identical count(), but this time outside of the 2nd foreach statement, I get an incorrect value of 0. This is the problem, if it wasn't clear before.

public function getRecentDiscussions($num_recent_discussions, $course_id) {
    //
    $this->load->database();
    //
    $recent_discussions_array = array();
    //
    // Construct query to fetch recent discussions along with their replies and some
    // basic user info about the authors
    $query_recent_discussions = $this->db->select('course_discussion.id AS course_discussion_id,
                                                   user.f_name,
                                                   user.l_name,
                                                   course_discussion.text,
                                                   course_discussion.posted_datetime,
                                                   course_discussion.is_reply,
                                                   course_discussion.parent_id
                                                  ')
                                         ->join('user', 'course_discussion.owner = user.id')
                                         ->where('course_discussion.course', $course_id)
                                         ->limit($num_recent_discussions)
                                         ->get('course_discussion');
    //
    foreach($query_recent_discussions->result_array() as $row) {
        //
        // Figure out of this comment is a parent or a reply. If it is a parent (meaning is_reply
        // is equal to 0), then treat it like one
        if($row['is_reply'] == '0') {
            //
            $recent_discussion_each = array();
            //
            $recent_discussion_each['discussion_id'] = $row['course_discussion_id'];
            $recent_discussion_each['discussion_owner_f_name'] = $row['f_name'];
            $recent_discussion_each['discussion_owner_l_name'] = $row['l_name'];
            $recent_discussion_each['discussion_body'] = $row['text'];
            $recent_discussion_each['discussion_posted_datetime'] = $row['posted_datetime'];
            $recent_discussion_each['discussion_replies_array'] = array();
            //
            array_push($recent_discussions_array, $recent_discussion_each);
        }
        //
        // Else, it must be a reply since is_reply is not a 0
        else {
            //
            // Look for the parent comment by going through the entire list of comments
            foreach($recent_discussions_array as $potential_parent) {
                //
                // Check to see if this comment's (now known as a reply's) id matches 
                // the id of the comment currently in the position in the list of comments
                if($row['parent_id'] == $potential_parent['discussion_id']) {
                    //
                    $reply_each = array();
                    //
                    $reply_each['reply_id'] = $row['course_discussion_id'];
                    $reply_each['reply_owner_f_name'] = $row['f_name'];
                    $reply_each['reply_owner_l_name'] = $row['l_name'];
                    $reply_each['reply_text'] = $row['text'];
                    $reply_each['reply_posted_datetime'] = $row['posted_datetime'];
                    $reply_each['reply_is_reply'] = $row['is_reply'];
                    $reply_each['reply_parent_id'] = $row['parent_id'];
                    //
                    array_push($potential_parent['discussion_replies_array'], $reply_each);
                }
            }
        }
    }
    //
    foreach($recent_discussions_array as $recent_discussion) {
        echo ($recent_discussion['discussion_id'].' has the following replies: ');
        foreach($recent_discussion['discussion_replies_array'] as $reply) {
            echo($reply['reply_id']);
        }
    }
    //
    return $recent_discussions_array;
    //
    // end
    //
}

Answer 1

foreach creates a copy of items for usage inside the loop body. What this means is that $potential_parent is not actually the original arrays from $recent_discussions_array , but copies of them.

Thus, when you modify them, as soon as the foreach($recent_discussions_array as $potential_parent) loop finishes, those copies go away.

As a simplified example of what I mean, note the distinct lack of any "baz" printing here:

http://ideone.com/WlDru

Then compare to what happens if you actually access the original array by key:

http://ideone.com/etvr5

What you really probably want, as Ben points out in the comments, is to use the & operator:

http://ideone.com/2TphI