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6 years ago
I find it that this is an ideal place to apply the spaceship operator, but it was not used in the examples. 

Here is Example#1 using the spaceship operator in the comparison function. 

    <?php
    // Arrays to compare
    $array1 = array(new stdclass, new stdclass,
                    new stdclass, new stdclass,
                   );

    $array2 = array(
                    new stdclass, new stdclass,
                   );

    // Set some properties for each object
    $array1[0]->width = 11; $array1[0]->height = 3;
    $array1[1]->width = 7;  $array1[1]->height = 1;
    $array1[2]->width = 2;  $array1[2]->height = 9;
    $array1[3]->width = 5;  $array1[3]->height = 7;

    $array2[0]->width = 7;  $array2[0]->height = 5;
    $array2[1]->width = 9;  $array2[1]->height = 2;

    function compare_by_area($a, $b) {
        $areaA = $a->width * $a->height;
        $areaB = $b->width * $b->height;
    
        return $areaA <=> $areaB;
    }

    print_r(array_udiff($array1, $array2, 'compare_by_area'));
    ?>

The output is:
    Array
    (
        [0] => stdClass Object
            (
                [width] => 11
                [height] => 3
            )
    
        [1] => stdClass Object
            (
                [width] => 7
                [height] => 1
            )
    
    )

I find it is pretty awesome you can substitute all of these lines:
    if ($areaA < $areaB) {
        return -1;
    } elseif ($areaA > $areaB) {
        return 1;
    } else {
        return 0;
    }

with just:

    return $areaA <=> $areaB;

Neat!
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