如何根据php中嵌套数组的第一个值对多维数组进行排序？

Question

I would like to sort a multidimensional array with respect to the first value of a nested array. For the example below the result should be [[1,3],[3, 6],[10, 20], [16, 19]]. I tried this but nothing happened. I would like to know where I am making a mistake using usort().

    function cmp($x, $y){
      global $arrint;
       if ($x[0] == $y[0]) {
       return 0;
        }
       return ($x[0] < $y[0]) ? -1 : 1;
        }

    $arrint = [
       [10, 20],
       [16, 19],
       [3, 6],
       [1,3]
    ];

    usort($arrint, "cmp");

Answer 1

You can make your sorting logic less verbose by using the spaceship operator ( <=> ).

$arrint = [
   [10, 20],
   [16, 19],
   [3, 6],
   [1,3]
];

usort($arrint, function ($a, $b) {
    return $a[0] <=> $b[0];
});

var_dump($arrint);