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up vote 2 down vote favorite

I currently have a problem within PHP where I want to sort these posts by their creation date so that they can then be shown in descending order. I have been looking for a PHP function to do this but have had no luck.

Is there an easy solution to this? Any idea will be greatly appreciated :)

array
      0 => 
        array
          'post_id' => string '1' (length=1)
          'user_id' => string '3' (length=1)
          'post' => string 'this is a post' (length=14)
          'created' => string '2012-04-05 20:11:38' (length=19)
     1 => 
        array
          'post_id' => string '2' (length=1)
          'user_id' => string '2' (length=1)
          'post' => string 'this is a post' (length=14)
          'created' => string '2012-04-05 20:11:38' (length=19)
     2 => 
        array
          'post_id' => string '3' (length=1)
          'user_id' => string '5' (length=1)
          'post' => string 'this is a post' (length=14)
          'created' => string '2012-04-05 20:11:38' (length=19)
share|improve this question
3  
Is this coming from a database? If not, why not? – NullUserException♦ Apr 5 '12 at 19:26
from where is this array being loaded? – hjpotter92 Apr 5 '12 at 19:27
3  
Yep, looks suspiciously like MySQL query rows. ORDER BY created DESC – Michael Berkowski Apr 5 '12 at 19:27
It is coming from a database but because i have to grab the posts of each user seperately im trying to combine it... is there a better way of doing something like .... WHERE user_id = array(2,3,5) in MySQL? – Daniel West Apr 5 '12 at 19:37
2  
That's hard to say if we can't see your query. WHERE user_id IN (2,3,5) is valid in MySQL – Arjan Apr 5 '12 at 19:43

4 Answers

up vote 2 down vote accepted

Try this:

<?php
$a=array(
      0 => 
        array(
          'post_id' => '1',
          'user_id' => '3',
          'post' => 'this is a post',
          'created' => '2012-04-05 20:11:40'
          ),
     1 => 
        array(
          'post_id' => '2',
          'user_id' => '2',
          'post' => 'this is a post',
          'created' => '2012-04-05 20:11:39'
          ),
     2 => 
        array(
          'post_id' => '3',
          'user_id' => '5',
          'post' => 'this is a post',
          'created' => '2012-04-05 20:11:38'
          )
);
function cmp($a,$b){
    return strtotime($a['created'])<strtotime($b['created'])?1:-1;
};

uasort($a,'cmp');
print_r($a);
?>
share|improve this answer
cmp() should return a negative value if $a is considered smaller than $b, a positive value if $a is greater than $b and 0 if they are equal. – Arjan Apr 5 '12 at 19:41
thanks, answer updated (i left out the equal case, i know..) – stewe Apr 5 '12 at 19:45
up vote 1 down vote

You can use strtotime() to convert the timestamp to an integer.

share|improve this answer
2  
And how's that going to help sort the 2D array? – Michael Berkowski Apr 5 '12 at 19:28
Heh ok, vague question. I thought OP was implying his stamps were Y-d-m. – Alex Howansky Apr 5 '12 at 19:31
1  
If the dates are in Y-d-m format, you can't easily convert them to timestamps. And if they are in Y-m-d format, you don't need to convert them. – Arjan Apr 5 '12 at 19:33
up vote 1 down vote

You can use the usort() function which allows you to sort an array based on your own criteria.

function cmp($a, $b)
{
    if ($a['created'] == $b['created']) {
        return 0;
    }

    return ($a['created'] < $b['created']) ? 1 : -1;
}

usort($myArray, "cmp");

print_r($myArray);

Or if you want to convert to a time:

function cmp($a, $b)
{
    if ($a['created'] == $b['created']) {
        return 0;
    }

    $aInt = strtotime($a['created']);
    $bInt = strtotime($b['created']);

    return ($aInt < $bInt) ? 1 : -1;
}
share|improve this answer
up vote 1 down vote

You can sort an array using a custom sort function, like so:

function cmp($a, $b) {
    if($a['created'] < $b['created']) {
        return 1;
    } else if ($a['created'] > $b['created']) {
        return -1;
    } else  {
        // The only option left is that they are equal
        return 0;
    }
}

usort($array, cmp);

For more information about usort, check the php manpage

share|improve this answer
1  
This will produce an ascending order rather than descending. – MrCode Apr 5 '12 at 19:44
1  
I updated my answer. Fortunately it's only a small change. – Arjan Apr 5 '12 at 19:48

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