Comparing Arrays of Objects by Column Values Using Array Functions

Many programming languages offer built-in functions for comparing arrays. However, these functions typically work with primitive data types and arrays, not arrays of objects. This raises the question of how to compare arrays of objects based on a specific property or column.

To address this, PHP provides array_udiff, a function that enables the comparison of arrays of objects by specifying a custom comparison function. Consider the following example:

$first_array = array(
    (object) ['id' => '205', 'day_id' => '12'],
    (object) ['id' => '210', 'day_id' => '15']
);

$second_array = array(
    (object) ['id' => '205', 'day_id' => '12'],
    (object) ['id' => '215', 'day_id' => '18']
);

To compare these arrays based on the 'id' property, you can use an anonymous function as follows:

$diff = array_udiff($first_array, $second_array,
    function ($obj_a, $obj_b) {
        return $obj_a->id - $obj_b->id;
    }
);

This function subtracts the 'id' values of the two objects to determine the difference. The resulting $diff will contain the objects in the first array that do not have a matching 'id' value in the second array.

In summary, by employing the array_udiff function and defining a custom comparison function, developers can compare arrays of objects based on specific properties or columns, providing flexibility in data analysis tasks.