Sort a PHP array by another array order and date

Was wondering if there is a way to sort (usort or equiv) an array based on key order of another array and date. I know how to do basic date sorting with usort, but was wondering if you could do both in one shot.

$cats = array(1,6,3,4,7,2);
$prods = array(
 array('cat'=>1,'date'=>'1/3/2011'),
 array('cat'=>2,'date'=>'1/6/2011'),
 array('cat'=>3,'da开发者_Go百科te'=>'2/3/2011')
);

I want $prods sorted by the category order of $cats and date order of $prods

Pay attention to your low accept rate, as it can deter people from taking the time to answer your questions. Remember to mark valid answers as accepted or otherwise post a comment to them explaining why they aren't valid.

This solution works fine in php 5.3+, if you are trapped in an older version you can easily replace DateTime objects with calls to strptime.

Products with a category that has no position specified are pushed to the end of the list (see product with cat == 42 in the example).

$cats = array(1,6,3,4,7,2);

// added a few products to test the date sorting
$prods = array(
  array('cat'=>1,'date'=>'3/3/2011'),
  array('cat'=>1,'date'=>'2/3/2011'),
  array('cat'=>1,'date'=>'1/3/2011'),
  array('cat'=>42,'date'=>'2/3/2011'),
  array('cat'=>2,'date'=>'1/3/2011'),
  array('cat'=>2,'date'=>'2/3/2011'),
  array('cat'=>2,'date'=>'1/6/2011'),
  array('cat'=>3,'date'=>'2/3/2011')
);

// need an index of category_id => position wanted in the sort
$r_cats = array_flip($cats);
// if the category of a product is not found in the requested sort, we will use 0, and product with category id 0 will be sent to the end of the sort
$r_cats[0] = count($r_cats);
// this one is needed for DateTime, put whatever your timezone is (not important for the use we do of it, but required to avoid a warning)
date_default_timezone_set('Europe/Paris');

usort($prods, function($a, $b) use($r_cats) {
  $cat_a = isset($r_cats[$a['cat']]) ? $r_cats[$a['cat']] : $r_cats[0];
  $cat_b = isset($r_cats[$b['cat']]) ? $r_cats[$b['cat']] : $r_cats[0];

  if ($cat_a < $cat_b) {
    return -1;
  } elseif ($cat_a > $cat_b) {
    return 1;
  }

  $date_a = DateTime::createFromFormat('j/n/Y', $a['date']);
  $date_b = DateTime::createFromFormat('j/n/Y', $b['date']);

  if ($date_a < $date_b) {
    return -1;
  } elseif ($date_a > $date_b) {
    return 1;
  }

  return 0;
});

var_dump($prods);

The results are as follow:

array(8) {
  [0]=>
  array(2) {
    ["cat"]=>
    int(1)
    ["date"]=>
    string(8) "1/3/2011"
  }
  [1]=>
  array(2) {
    ["cat"]=>
    int(1)
    ["date"]=>
    string(8) "2/3/2011"
  }
  [2]=>
  array(2) {
    ["cat"]=>
    int(1)
    ["date"]=>
    string(8) "3/3/2011"
  }
  [3]=>
  array(2) {
    ["cat"]=>
    int(3)
    ["date"]=>
    string(8) "2/3/2011"
  }
  [4]=>
  array(2) {
    ["cat"]=>
    int(2)
    ["date"]=>
    string(8) "1/3/2011"
  }
  [5]=>
  array(2) {
    ["cat"]=>
    int(2)
    ["date"]=>
    string(8) "2/3/2011"
  }
  [6]=>
  array(2) {
    ["cat"]=>
    int(2)
    ["date"]=>
    string(8) "1/6/2011"
  }
  [7]=>
  array(2) {
    ["cat"]=>
    int(42)
    ["date"]=>
    string(8) "2/3/2011"
  }
}