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Comparing two arrays of objects with array_udiff

Array 1: $ tags_result

    array (size=4)
  0 => 
    object(stdClass)[8]
      public 'id_tag' => string '2' (length=1)
      public 'tag' => string 'tag 1' (length=5)
  1 => 
    object(stdClass)[9]
      public 'id_tag' => string '5' (length=1)
      public 'tag' => string 'tag 4' (length=5)
  2 => 
    object(stdClass)[10]
      public 'id_tag' => string '6' (length=1)
      public 'tag' => string 'tag 7' (length=5)
  3 => 
    object(stdClass)[11]
      public 'id_tag' => string '7' (length=1)
      public 'tag' => string 'tag 9' (length=5)

Array 2: $ post_tags_result

    array (size=2)
  0 => 
    object(stdClass)[5]
      public 'id_tag' => string '2' (length=1)
      public 'tag' => string 'tag 1' (length=5)
  1 => 
    object(stdClass)[6]
      public 'id_tag' => string '6' (length=1)
      public 'tag' => string 'tag 7' (length=5)

I am trying to extract the values ​​of array 1 that are not displayed in array 2:

function foo($tags_result, $post_tags_result){
    return $tags_result->id_tag != $post_tags_result->id_tag;
}

$difference_tags = array_udiff($tags_result, $post_tags_result, 'foo');

But the result returns a common value: tag 1. I expect only tag 4 and tag 9.

    array (size=3)
  0 => 
    object(stdClass)[8]
      public 'id_tag' => string '2' (length=1)
      public 'tag' => string 'tag 1' (length=5)
  1 => 
    object(stdClass)[9]
      public 'id_tag' => string '5' (length=1)
      public 'tag' => string 'tag 4' (length=5)
  3 => 
    object(stdClass)[11]
      public 'id_tag' => string '7' (length=1)
      public 'tag' => string 'tag 9' (length=5)
+4
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2 answers

Alternatively, you can collect all the tags that you want to exclude first. Then after that you can filter it through array_filterand get the desired result. Example:

$tags = array();
foreach($post_tags_result as $t) {
    $tags[] = $t->tag; // gather all tags
}
// filter array using gathered tags
$result = array_filter($tags_result, function($v) use($tags){
    return !in_array($v->tag, $tags);
});

Output example

+4
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From the manual:

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered less than, equal to or greater than the second.

, diff . , - :

$ php -a

php > $a = [['id'=>1],['id'=>2],['id'=>3],['id'=>4]];
php > $b = [['id'=>1],['id'=>4]];
php > $c = array_udiff($a, $b, function($a, $b){ 
               return $a['id'] - $b['id']; 
           });
php > print_r($c);
Array
(
    [1] => Array
        (
            [id] => 2
        )

    [2] => Array
        (
            [id] => 3
        )

)

:

$difference_tags = array_udiff($tags_result, $post_tags_result, function(($a1, $a2){
    return $a1->id_tag - $q2->id_tag;
}));
0

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