Find matching items in array

Question

Absolutely doing my head in here over something that I'm sure is very simple...

I have 2 arrays.

$post_cats which are categories that any given post is in.
$ad_cats which is an array of categories in which ads are placed.

Basically, if a post has in its array of selected categories, a category that matches an item in the array of ad categories, then it must return the matching value/item.

$post_cats returns this

array(4) {    
  [0]=> array(1) { ["slug"]=> string(6) "energy" }    
  [1]=> array(1) { ["slug"]=> string(6) "global" }  
  [2]=> array(1) { ["slug"]=> string(8) "identify" }  
  [3]=> array(1) { ["slug"]=> string(5) "south" }  
}

and $ad_cats returns this

array(6) {   
  [0]=> array(1) { ["slug"]=> string(5) "north" }  
  [1]=> array(1) { ["slug"]=> string(5) "south" }  
  [2]=> array(1) { ["slug"]=> string(4) "east" }  
  [3]=> array(1) { ["slug"]=> string(4) "west" }  
  [4]=> array(1) { ["slug"]=> string(6) "global" }  
  [5]=> array(1) { ["slug"]=> string(8) "fallback" }  
}

The duplicated item there is "south", so in my mind the value of array_intersect($post_cats, $ad_cats); should be an array with a single item - "south", correct?

But its returning, what seems like, everything in either of the arrays... I can't for the life of me get it to work..

Using the above example, I need to return "south" to a variable.

`array_intersect` will not work how you are expecting with multidimensional arrays. — nickb, Mar 08 '13 at 21:18
@nickb ok, so can you assist me in what i *should* be using? — Mark, Mar 08 '13 at 21:22

Buksy · Accepted Answer · 2013-03-08T21:28:54.493

0

So you are looking for items that are in both arrays? ...

What about something like this:

function find_duplicate($array1, $array2)
{
  $list = array();

  foreach($array1 as $value1)
  {
    foreach($array2 as $value2)
    {
     if($value1 == $value2) $list[] = $value1;
    }
  }

  return $list;
}

edited Mar 08 '13 at 21:28

answered Mar 08 '13 at 21:23

Buksy

11,571
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1

This has more syntax errors than a script written by my cat jumping on the keyboard. – Shoe Mar 08 '13 at 21:24
2

Still wrong. You are treating those arrays as one dimensional arrays, they are bi-dimensional. – Shoe Mar 08 '13 at 21:30
1

@Jueecy: yes, I have to admit I haven't fully read the question, just quickly written the example ... but seems like it does work for Mark, if not, let me know I will update it ... – Buksy Mar 08 '13 at 21:34

score 0 · Answer 2 · answered Mar 08 '13 at 21:33

The best way is to convert those arrays in arrays array_intersect can work with. Considering:

$a; // first array
$b; // second array

then you would go with:

$a1 = array();
foreach ($a as $v) $a1[] = $v['slug'];

$b1 = array();
foreach ($b as $v) $b1[] = $v['slug'];

$c = array_intersect($a1, $b1);

PHP functions usually work with more powerful algorithms than what you may think; therefore it's a good choice to let PHP functions handle this kind of things.

Olaf Dietsche · Answer 3 · 2013-03-08T21:50:26.677

0

This solution uses array_map to get at the values and takes the intersection of that

function mapper($a) 
{
    return $a['slug'];
}

$set1 = array_map('mapper', $post_cats);
$set2 = array_map('mapper', $ad_cats);
$result = array_intersect($set1, $set2);

PhpFiddle for testing.

edited Mar 08 '13 at 21:50

answered Mar 08 '13 at 21:41

Olaf Dietsche

72,253
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Find matching items in array

3 Answers3