Sort array by value

Question

I am creating a "Pinned" feature for my forum and I am looking for a way to put my pinned topics at the beginning of the array so that they are "stuck" to the top of the page.

If the topic is not pinned then topic_pinned=NULL if it is pinned then topic_pinned=0.

The array is sorted by topic_updated. The pinned topics need to stay sorted by topic_updated while staying at the top of the page, and then under the pinned topics are the non-pinned topics, which are also sorted by topic_updated.

Topic Array ($forum_topic_results):

Array
(
    [0] => Array
        (
            [topic_id] => 4
            [topic_subject] => Test Subject #4
            [topic_date] => 2015-09-10 18:34:18
            [topic_by] => 1
            [topic_pinned] => 
            [topic_updated] => 2015-09-10 20:37:22
        )

    [1] => Array
        (
            [topic_id] => 3
            [topic_subject] => Test Subject #3
            [topic_date] => 2015-08-22 09:24:40
            [topic_by] => 1
            [topic_pinned] => 0
            [topic_updated] => 2015-09-04 22:02:31
        )

    [2] => Array
        (
            [topic_id] => 2
            [topic_subject] => Test Subject #2
            [topic_date] => 2015-08-15 10:56:00
            [topic_by] => 1
            [topic_pinned] => 
            [topic_updated] => 2015-09-04 19:45:32
        )

    [3] => Array
        (
            [topic_id] => 1
            [topic_subject] => Test Subject #1
            [topic_date] => 2015-08-30 19:48:17
            [topic_by] => 1
            [topic_pinned] => 0
            [topic_updated] => 2015-09-03 00:44:38
        )
)

PHP:

/**
 * getAllTopics
 *
 * Retreives the topics of the chosen category from the `forum_topics` table.
 *
 * @param   $cat_id
 * @access  public
 */
public function getAllTopics($cat_id=NULL)
{
    $database=$this->database;

    $database->query('SELECT topic_id, topic_subject, topic_date, topic_by, topic_pinned, topic_locked FROM forum_topics WHERE topic_cat = :catid ORDER BY topic_updated DESC', array(':catid' => $cat_id));
    $result = $database->statement->fetchAll(PDO::FETCH_ASSOC);

    return $result;
}

# Get topics
$forum_topic_results = $this->getAllTopics($_GET['cat']);
foreach($forum_topic_results as $forum_topic_row)
{
    # Get user's username.
    $topic_by=SearchUser($forum_topic_row['topic_by']);

    $data.='<tr>'.
        '<td>'.
            '<h3><a href="'.$_SERVER['PHP_SELF'].'?action=forum_posts&topic='.$forum_topic_row['topic_id'].'">'.$forum_topic_row['topic_subject'].'</a></h3>'.
            'by '.$topic_by['username'].' on '.date('D M d, Y g:i a', strtotime($forum_topic_row['topic_date'])).
        '</td>'.
    '</tr>';
}

Outcome I want:

Array
(
    [0] => Array
        (
            [topic_id] => 3
            [topic_subject] => Test Subject #3
            [topic_date] => 2015-08-22 09:24:40
            [topic_by] => 1
            [topic_pinned] => 0
            [topic_updated] => 2015-09-04 22:02:31
        )

    [1] => Array
        (
            [topic_id] => 1
            [topic_subject] => Test Subject #1
            [topic_date] => 2015-08-30 19:48:17
            [topic_by] => 1
            [topic_pinned] => 0
            [topic_updated] => 2015-09-03 00:44:38
        )

    [2] => Array
        (
            [topic_id] => 4
            [topic_subject] => Test Subject #4
            [topic_date] => 2015-09-10 18:34:18
            [topic_by] => 1
            [topic_pinned] => 
            [topic_updated] => 2015-09-10 20:37:22
        )

    [3] => Array
        (
            [topic_id] => 2
            [topic_subject] => Test Subject #2
            [topic_date] => 2015-08-15 10:56:00
            [topic_by] => 1
            [topic_pinned] => 
            [topic_updated] => 2015-09-04 19:45:32
        )
)

What do you want and what is expected outcome? Also what you tried so for? please paste your code effort also.THANKS. — Alive to die - Anant, Sep 11 '15 at 05:07
possible duplicate of [Reference: all basic ways to sort arrays and data in PHP](http://stackoverflow.com/questions/17364127/reference-all-basic-ways-to-sort-arrays-and-data-in-php) — scrowler, Sep 11 '15 at 05:09
Also, do you store this data in a database? It would be trivial to retrieve the data ordered in advance and then there would be no need to sort. — gview, Sep 11 '15 at 05:12
I feel dumb. I just had to change my query to use `ORDER BY topic_pinned DESC, topic_updated DESC` — Draven, Sep 11 '15 at 05:26

M0rtiis · Accepted Answer · 2015-09-11T05:15:56.987

4

Do antother way.

Mark in your database table PINNED as 1.

NOT PINNED as 0.

After that just add (replace ORDER BY) to your query where u select topics:

ORDER BY `topic_pinned` DESC, `topic_updated` DESC

edited Sep 11 '15 at 05:15

answered Sep 11 '15 at 05:10

M0rtiis

3,676
1
15
22

Does not account for the date! – Aziz Saleh Sep 11 '15 at 05:11
really? the point is to stay pinned topics on the top. u read only about how to sort an array. but i provided solution how to avoid this (with ONE line of code) by passing logic to sql. – M0rtiis Sep 11 '15 at 05:13
No his point is, that you would need at least ORDER BY topic_pinned, topic_updated – gview Sep 11 '15 at 05:14
Leaving `topic_pinned=NULL` works just fine. Thank you! – Draven Sep 11 '15 at 05:28

score 1 · Answer 2 · answered Sep 11 '15 at 06:08

Just for completeness, if you actually still wanted or needed to do this to the arrays via php I'd probably opt for using usort. It doesn't require manufacturing columnar arrays.

usort lets you write either a function or provide an anonymous function that does the comparison logic. Since you have an array of arrays, and the comparison needs to be done utilizing several array elements, you could easily write a simple comparison function so long as you keep in mind that:

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

Something like this (off the cuff, untested code)

function cmp($a, $b) {
    if ($a['topic_pinned'] == $b['topic_pinned']) {
        // Have to compare Dates
        $adate = new DateTime($a['topic_updated']);
        $bdate = new DateTime($b['topic_updated']);
        return ($adate < $bdate) ? -1 : 1;
    } elseif ($a['topic_pinned'] == null) {
        return 1;
    } else {
        return -1;
    }  
}

usort($array, 'cmp');

As you can see this gets complicated fast, due to the need to convert the datetime strings into datetime objects so that you can actually do comparisons.

All the more reason why using the sql database is better/faster/easier in this circumstance.

Pathik Vejani · Answer 3 · 2015-09-11T05:20:20.053

0

This should work:

<?php
$finalArr = $forum_topic_results;
foreach ($finalArr as $key => $row) {
    $topic_pinned[$key] = $row['topic_pinned'];
}
array_multisort($topic_pinned, SORT_DESC, $finalArr);
return $finalArr;
?>

more information about an array_multisort: array_multisort

edited Sep 11 '15 at 05:20

answered Sep 11 '15 at 05:14

Pathik Vejani

4,263
8
57
98

I did not know about `array_multisort()`, thank you. – Draven Sep 11 '15 at 05:29
Seems to me this is missing the comparison of topic_updated. If the data is pre-supposed to already be sorted by date, this is probably ok however. – gview Sep 11 '15 at 06:12
@gview yes.. this should also work.. but if possible then we should only use query.. – Pathik Vejani Sep 11 '15 at 07:55

Sort array by value

3 Answers3