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18

How can I sort this array of objects by one of its fields, like name or count ?

  Array
(
    [0] => stdClass Object
        (
            [ID] => 1
            [name] => Mary Jane
            [count] => 420
        )

    [1] => stdClass Object
        (
            [ID] => 2
            [name] => Johnny
            [count] => 234
        )

    [2] => stdClass Object
        (
            [ID] => 3
            [name] => Kathy
            [count] => 4354
        )

   ....
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5 Answers

up vote 61 down vote accepted

Use usort, here's an example adapted from the manual:

function cmp($a, $b)
{
    return strcmp($a->name, $b->name);
}

usort($your_data, "cmp");
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up vote 51 down vote

Heres a nicer way using closures

usort($your_data, function($a, $b)
{
    return strcmp($a->name, $b->name);
});

Please note this is not in PHP's documentation but if you using 5.3+ closures are supported where callable arguments can be provided.

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1  
I love this one better than the accepted answer since we can quickly define the compare function and can use in a class – Nam G. VU May 1 '12 at 18:43
This worked for me, however the accepted answer did not. The class would not recognize the callback function by name. I am not sure why. Thanks – I am John Galt Sep 5 '12 at 15:25
@IamJohnGalt - Maybe this is relevant: look this comment on php.net – Bruno May 28 at 22:39
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up vote 6 down vote 
usort($array, 'my_sort_function');

var_dump($array);

function my_sort_function($a, $b)
{
    return $a->name < $b->name;
}

The same code will be with the count field.

More details about usort: http://ru2.php.net/usort

Btw, where did you get that array from? I hope that not from database?

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Actually $result will contain TRUE if it's successful, and your comparison should be $a->name > $b->name. :) – cambraca Nov 26 '10 at 3:56
1  
@cambraca: oh, forgot it accepts array by reference. Btw, OP did not said which order he need to sort collection. – zerkms Nov 26 '10 at 3:57
well yes, it's a database :) actually from a function that gets the data from the database – Alex Nov 26 '10 at 4:01
1  
@Alex: why don't you sort it in database then? ORDER BY count – zerkms Nov 26 '10 at 4:02
it's more complicated, because that's a stadard function part of wordpress, and as I'm writing a plugin, I can't change wp files. I tried your example using create_function (because I'm using it inside a class and I don't know how to pass the function name to usort): create_function('$a,$b', "return $a->count < $b->count;") but I can't make it work :( I get a few notices and warning that usort expects parameter 2 to be a valid callback – Alex Nov 26 '10 at 4:11
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up vote 5 down vote

if you're using php oop you might need to change to:

public static function cmp($a, $b) 
{
    return strcmp($a->name, $b->name);
}

usort($your_data, array('YOUR_CLASS_NAME','FUNCTION_NAME'); //in this case function_name = cmp
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Excelent !!!!!! – ramiromd Jun 5 at 16:05
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up vote 0 down vote

If you need local based string comparison, you can use strcoll instead of strcmp.

Remeber to first use setlocale with LC_COLLATE to set locale information if needed.

  usort($your_data,function($a,$b){
    setlocale (LC_COLLATE, 'pl_PL.UTF-8'); // Example of Polish language collation
    return strcoll($a->name,$b->name);
  });
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