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I'm having trouble sorting an array according to another array. I've tried usort, uksort and uasort but I'm getting nowhere. Other questions on stackoverflow are not directly applicable here, as my array structure is different. I want to sort this multidimensional array:

$main = Array (
    [Technology] => Array ()
    [World] => Array ()
    [Europe] => Array () 
)

By using this index-array:

$index = Array (
    [0] => Europe
    [1] => Technology
    [2] => World
)

Basically, in this example I would want Europe to come first in the $main array, Technology second and World third, as this is their positioning in the $index array. How do I do that? (Please disregard little syntax errors in the arrays above)

share|improve this question
    
Have you tried ksort? –  bsdnoobz May 22 '12 at 12:50
    
Can you use array_multisort over here? It is usually used to sort multi-dimensional arrays. But herein you still need to do some initial processing of your arrays.. php.net/manual/en/function.array-multisort.php –  verisimilitude May 22 '12 at 12:52

3 Answers 3

up vote 1 down vote accepted 
$main_sort = array()    
foreach ($index as $key => $value) {
    if ($main [$value]) $main_sorted [$value] = $main [$value];
}

Simply loop through the $index array and map those values to a new array using the values from the $main array.

share|improve this answer
    
it works. thanks –  Tomi Seus May 23 '12 at 18:05
    
if $index contains values that are not keys of $main, you get nulls in $main_sorted and possibly warnings in your log –  Walter Tross May 29 '12 at 8:35
    
Fixed by adding a simple if-statement –  Jeroen May 29 '12 at 8:45
up vote 0 down vote

This solution works if you don't have any value in $index which is not a key in $main (as is the case in your example):

$sorted = array_merge(array_flip($index), $main);

If the values of $index are a superset of the keys of $main, a possible solution is:

$sorted = array_intersect_assoc(array_merge(array_flip($index), $main), $main);

Keep in mind that letting PHP functions work on arrays is much faster than doing so "explicitly"

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up vote 0 down vote

Given $index and $main, 

uksort($main, function ($k, $k2) use ($index) {
  return array_search($k, $index) - array_search($k2, $index);
});

Array will be sorted according to keys specified in $index. Behavior of not-matched keys is unspecified.

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