Multidimensional php array error

Question

I’m trying to find the difference between multidimensional arrays but presents these errors:

Notice: Array to string Conversion in C: server htdocs System tests.php on line 319

Notice: Array to string Conversion in C: server htdocs System tests.php on line 319

Could someone help me?

$array_1 = array(
    array( 'nome' => 'Alexandre',   'idade' => '65' ),
    array( 'nome' => 'camila',    'idade' => '33' ),
    array( 'nome' => 'Zezinha', 'idade' => '29' ),
    array( 'nome' => 'Rosana',  'idade' => '64' )
);
$array_2 = array(
    array( 'nome' => 'Alexandre',   'idade' => '65' ),
    array( 'nome' => 'camila',    'idade' => '33' )
);
print_r( array_diff_assoc( $array_1, $array_2) );

Answer 1

The difference between array_diff and array_diff_assoc is that the second compares the index as well. In your case, how are two arrays numerical index (sometimes called sequential) where apparently no matter what index the value is. If Alexandre/65 is the first in a array and the last one on the other makes no difference, it’s the same record, so should utilise array_diff.

However, as stated in official documentation:

Note:

Two elements are considered equal if and only if, (string) $elem1 === (string) $elem2. In words: when the representation of string is the same.

And this is where the problem lies. Its elements are array and cannot be converted to string in this way; and that is what justifies the error message you had:

Notice: Array to string Conversion in ...

Why does language compare values like string? I don’t know, there must be some reason (or not...). To solve this you must do it manually:

$diff = [];

foreach ($array_1 as $arr) {
    if (!in_array($arr, $array_2)) {
        $diff[] = $arr;
    }
}

print_r($diff);

With that the way out would be:

Array
(
    [0] => Array
        (
            [nome] => Zezinha
            [idade] => 29
        )

    [1] => Array
        (
            [nome] => Rosana
            [idade] => 64
        )

)

The function in_array is based on the loose comparison between the elements, ==, but you can use the restricted, ===, if the third parameter, strict, is defined as true.

---

An alternative is to manually implement the comparison function and use array_udiff:

function compare_array($a, $b)
{
  return $a <=> $b;
}

$diff = array_udiff($array_1, $array_2, 'compare_array');

The result would be the same. With anonymous function would be:

$diff = array_udiff($array_1, $array_2, function ($a, $b) {
  return $a <=> $b;
});