up vote 0 down vote favorite

I did look at usort, but am still a little confused...

Here is what the $myobject object looks like:

Array
(
    [0] => stdClass Object
        (
            [tid] => 13
            [vid] => 4
        )

    [1] => stdClass Object
        (
            [tid] => 10
            [vid] => 4
        )

    [2] => stdClass Object
        (
            [tid] => 34
            [vid] => 4
        )

    [3] => stdClass Object
        (
            [tid] => 9
            [vid] => 4
        )

I saw this: 

function cmp( $a, $b )
{ 
  if(  $a->weight ==  $b->weight ){ return 0 ; } 
  return ($a->weight < $b->weight) ? -1 : 1;
} 
usort($myobject,'cmp');

I'm trying to sort according to tid, but, I guess I'm just not sure really if I have to change weight to something? Or will it just work as is? I tried it, but nothing outputted...

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2 Answers

up vote 4 down vote accepted

cmp is the a callback function that usort uses to compare complex objects (like yours) to figure out how to sort them. modify cmp for your use (or rename it to whatever you wish)

function cmp( $a, $b )
{ 
  if(  $a->tid ==  $b->tid ){ return 0 ; } 
  return ($a->tid < $b->tid) ? -1 : 1;
} 
usort($myobject,'cmp');

function sort_by_tid( $a, $b )
{ 
  if(  $a->tid ==  $b->tid ){ return 0 ; } 
  return ($a->tid < $b->tid) ? -1 : 1;
} 
usort($myobject,'sort_by_tid');

http://www.php.net/usort

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Ok, thanks for explaining that, but it's still not working... Am I not allowed to assign that to a variable or something? Because when I do $myobject = usort($myobject, 'cmp'), it doesn't output anything at all? I'm assuming I just need one or the other functions from above, and not both, since they both do the same thing? – andy787899 Feb 18 '10 at 6:05
Also, I did also try renaming the two variables to $myobject1 and $myobject2 = usort... but that didn't work either... – andy787899 Feb 18 '10 at 6:06
Nevermind! Should have just tried not assigning it before posting... thanks! – andy787899 Feb 18 '10 at 6:09
usort is one of the few php functions that takes a pointer as an input (very C-ish in style) and returns a boolean. check out the PHP documentation page. try just putting usort($myobject, 'cmp') and then checking what $myobject has. – scootklein Feb 18 '10 at 6:09
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up vote 0 down vote

usort function uses the quick sort function.

refer this url for more clear explaination:

http://www.programmerphp.com/article/php/23012010/how-does-usort-works-php.html

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