Question

How would I re-order an array of objects like:

Array
(
    [0] => stdClass Object
        (
            [term_id] => 3
            [name] => Name
        )
    [1] => stdClass Object
        (
            [term_id] => 1
            [name] => Name2
        )
    [2] => stdClass Object
        (
            [term_id] => 5
            [name] => Name
        )
)

According to the objects term_id, against a custom defined array of ids:

$order_by = array( 5,3,1 )

What I’m using now is below, but I feel like I’m not taking advantage of some advanced sorting functions PHP has… Can anyone tell me what would work better?

$sorted_terms = array();
$order_by = array( 5,3,1 );

foreach( $order_by as $id ) {
    foreach ( $terms as $pos => $obj ) {
        if ( $obj->term_id == $id ) {
            $sorted_terms[] = $obj;
            break;
        }
    }
}

Answer 1

Basically, the rank of your terms in their sorted order is the same as the rank of their corresponding ids, which happens to be the array keys in the $order_by array. So we just need to flip that array to get the mapping of ids to ranks, and then sort using it with a custom comparison function.

Here’s a simple code snippet that should work:

<?php

   $skeys = array_flip($order_by);
   usort($terms,
             function($a,$b) use ($skeys){$a =  $skeys[$a->term_id]; $b = $skeys[$b->term_id]; return $a - $b;});

The above code would work with PHP 5.3 or later.

Here’s the same thing with pre 5.3 PHP:

 <?php

   $skeys = array_flip($order_by);
   function sfun($a,$b){
       global $skeys;
       $a =  $skeys[$a->term_id]; $b = $skeys[$b->term_id]; return $a - $b;
   }

   usort($terms, "sfun");

The important functions are:

• array_flip
• usort