php sorting timestamp array

Question

I have an unexpected outcome of usort.

$ccpmail[] =  
    array(
            "mail_id"=>$evemailheader["mail_id"],
            "is_read"=>$evemailheader['is_read'],                                           
            "fromid"=>$evemailheader['from'],
            "fromname"=>$character_names[get_character_name($evemailheader['from'], $character_names)]['character_name'],
            "subject"=>$evemailheader['subject'],
            "labels"=>array("EVE Online"),
            'datestamp'=>strtotime($evemailheader['timestamp']),
            'date'=>$date
        );

$email[] =  
    array(
        "mail_id"=>$mailid,
        "is_read"=>$is_read,                                            
        "fromid"=>$message_parsed->getHeaderValue('from'),
        "fromname"=>$message_parsed->getHeader('from')->getPersonName(),
        "subject"=>$message_parsed->getHeaderValue('subject'),
        "labels"=>array("E-mail"),
        'datestamp'=>strtotime($message_parsed->getHeaderValue('date')),
        'date'=>$date->format('Y-m-d H:i:s')
    );


$allmail = array_merge($ccpmail, $email);

function sortByOrder($a, $b) {
return  $a['datestamp'] < $b['datestamp'];
}

usort($allmail, 'sortByOrder');
var_dump($allmail);

RESULTS IN:

array(133) {
[0]=>
array(8) {
    ["mail_id"]=>
    string(32) "bcfc5f6b0365738e58c99e0501b37210"
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    string(22) "EMAIL"
    ["fromname"]=>
    string(12) "NAME"
    ["subject"]=>
    string(4) "tset"
    ["labels"]=>
    array(1) {
        [0]=>
        string(6) "E-mail"
    }
    ["datestamp"]=>
    int(1485509147)
    ["date"]=>
    string(19) "2017-01-27 09:25:47"
}
[1]=>
array(8) {
    ["mail_id"]=>
    string(32) "317c556f35213548598f0bb838a237c1"
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    string(22) "EMAIL"
    ["fromname"]=>
    string(12) "NAME"
    ["subject"]=>
    string(5) "etest"
    ["labels"]=>
    array(1) {
        [0]=>
        string(6) "E-mail"
    }
    ["datestamp"]=>
    int(1485509066)
    ["date"]=>
    string(19) "2017-01-27 09:24:26"
}
[2]=>
array(8) {
    ["mail_id"]=>
    int(364172046)
    ["is_read"]=>
    bool(false)
    ["fromid"]=>
    int(90766569)
    ["fromname"]=>
    string(13) "NAME"
    ["subject"]=>
    string(2) "hi"
    ["labels"]=>
    array(1) {
        [0]=>
        string(10) "EVE Online"
    }
    ["datestamp"]=>
    int(1485507000)
    ["date"]=>
    object(DateTime)#3 (3) {
        ["date"]=>
        string(26) "2017-01-27 08:50:00.000000"
        ["timezone_type"]=>
        int(2)
        ["timezone"]=>
        string(1) "Z"
    }
}
[3]=>
array(8) {
    ["mail_id"]=>
    int(364160956)
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    int(793110520)
    ["fromname"]=>
    string(10) "NAME"
    ["subject"]=>
    string(30) "theres no brakes on this train"
    ["labels"]=>
    array(1) {
        [0]=>
        string(10) "EVE Online"
    }
    ["datestamp"]=>
    int(1485455100)
    ["date"]=>
    object(DateTime)#7 (3) {
        ["date"]=>
        string(26) "2017-01-26 18:25:00.000000"
        ["timezone_type"]=>
        int(2)
        ["timezone"]=>
        string(1) "Z"
    }
}
[4]=>
array(8) {
    ["mail_id"]=>
    int(364160959)
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    int(793110520)
    ["fromname"]=>
    string(10) "NAME"
    ["subject"]=>
    string(10) "safe word?"
    ["labels"]=>
    array(1) {
        [0]=>
        string(10) "EVE Online"
    }
    ["datestamp"]=>
    int(1485455100)
    ["date"]=>
    object(DateTime)#5 (3) {
        ["date"]=>
        string(26) "2017-01-26 18:25:00.000000"
        ["timezone_type"]=>
        int(2)
        ["timezone"]=>
        string(1) "Z"
    }
}
[5]=>
array(8) {
    ["mail_id"]=>
    int(364160957)
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    int(1228369447)
    ["fromname"]=>
    string(7) "NAME"
    ["subject"]=>
    string(4) "spam"
    ["labels"]=>
    array(1) {
        [0]=>
        string(10) "EVE Online"
    }
    ["datestamp"]=>
    int(1485455100)
    ["date"]=>
    object(DateTime)#6 (3) {
        ["date"]=>
        string(26) "2017-01-26 18:25:00.000000"
        ["timezone_type"]=>
        int(2)
        ["timezone"]=>
        string(1) "Z"
    }
}
[6]=>
array(8) {
    ["mail_id"]=>
    int(364160934)
    ["is_read"]=>
    bool(true)
    ["fromid"]=>
    int(94312752)
    ["fromname"]=>
    string(19) "NAME"
    ["subject"]=>
    string(4) "spam"
    ["labels"]=>
    array(1) {
        [0]=>
        string(10) "EVE Online"
    }
    ["datestamp"]=>
    int(1485455040)
    ["date"]=>
    object(DateTime)#11 (3) {
        ["date"]=>
        string(26) "2017-01-26 18:24:00.000000"
        ["timezone_type"]=>
        int(2)
        ["timezone"]=>
        string(1) "Z"
    }
}

As you can see the array is not sorted like how I want it. I want the lowest timestamp at top. Can anyone help me out?

return $a['datestamp'] > $b['datestamp'];?

u_mulder
– u_mulder

2017-01-27 21:40:02 +00:00
Commented Jan 27, 2017 at 21:40 — u_mulder
– u_mulder, Commented Jan 27, 2017 at 21:40
Did not work... the array sorted just like array_reverse()

S. R.
– S. R.

2017-01-27 22:00:17 +00:00
Commented Jan 27, 2017 at 22:00 — S. R.
– S. R., Commented Jan 27, 2017 at 22:00

Ulrik McArdle · Accepted Answer · 2017-01-27 21:55:59Z

1

If you use PHP7 or later, you could use the spaceship operator, like so:

function sortByOrder($a, $b) {
    return  $a['datestamp'] <=> $b['datestamp'];
}

This will sort it like you want. If not using PHP7 or higher, you would have to make some if statements to see if it's higher, lower or equal.

answered Jan 27, 2017 at 21:55

Ulrik McArdle

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Comments

Don't Panic · Accepted Answer · 2017-01-27 22:07:30Z

0

Your comparison function needs to return an integer greater than, less than or equal to zero in order to sort properly. (See the definition of value_compare_func here.) This expression:

return  $a['datestamp'] < $b['datestamp'];

will only return true or false (1 or 0,) neither of which is the correct value to sort earlier timestamps before later ones (-1).

You can add one more comparison so that it will the values necessary to sort correctly.

function sortByOrder($a, $b) {
    if ($a['datestamp'] < $b['datestamp']) return -1;    // return -1 if $a is earlier
    return  $a['datestamp'] > $b['datestamp'];    // return 1 if $a is later, or 0 if equal
}

As noted in the other answer, if you're using PHP 7 there is an operator (<=>) that will let you do this with one statement.

edited Jan 27, 2017 at 22:07

answered Jan 27, 2017 at 21:46

Don't Panic

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2 Comments

S. R. Over a year ago

This has exactly the same outcome unfortunatly

Don't Panic Over a year ago

Great! Glad to hear it.

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