How to Find the Difference Between Arrays of Objects Based on Column Values?

Finding the Difference Between Arrays of Objects Based on Column Values

Determining the differences between two arrays of objects can be challenging when using conventional array-comparison functions like array_diff or array_udiff. However, a custom function can be employed to facilitate the comparison of specific object properties.

Consider the following array of objects:

<code class="php">array(4) {
    [0]=>
        object(stdClass)#32 (9) {
            [&quot;id&quot;]=>
            string(3) &quot;205&quot;
            [&quot;day_id&quot;]=>
            string(2) &quot;12&quot;
        }
}</code>

To identify the difference between two such arrays based on the "id" column, a custom comparison function can be defined:

<code class="php">function compare_objects($obj_a, $obj_b) {
  return $obj_a->id - $obj_b->id;
}</code>

This function subtracts the "id" properties of two objects, resulting in a numerical value that indicates the difference between them.

The following code utilizes the compare_objects function to determine the difference between two arrays of objects:

<code class="php">$first_array = // Array of objects
$second_array = // Array of objects

$diff = array_udiff($first_array, $second_array, 'compare_objects');</code>

The array_udiff function compares the objects in the first and second arrays using the compare_objects function. The result, stored in $diff, contains the objects that are present in one array but not the other.

In PHP >= 5.3, an anonymous function can be used instead of a named function:

<code class="php">$diff = array_udiff($first_array, $second_array,
  function ($obj_a, $obj_b) {
    return $obj_a->id - $obj_b->id;
  }
);</code>

This streamlined approach achieves the same functionality as the compare_objects function. Utilizing these custom comparison methods enables the efficient identification of differences between arrays of objects based on specific column values.

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