how with php Get the density of points in the coordinate plane?

density_of_points.php

<?php
$points = [
    [3, 4], [7, 9], [12, 15], // Coordinates
    [18, 5], [20, 25]
];

$grid_size = 10;

$grid_density = [];

foreach ($points as $point) {
    $x = floor($point[0] / $grid_size);
    $y = floor($point[1] / $grid_size);
    $grid_key = "$x,$y";
    if (!isset($grid_density[$grid_key])) {
        $grid_density[$grid_key] = 0;
    }
    $grid_density[$grid_key]++;
}

foreach ($grid_density as $grid => $count) {
    echo "Grid $grid: $count points\n";
}