<?php
    header("Content-Type: text/html; charset=UTF-8");
    $dots=array(
        array(10,10),
        array(15,14),
        array(17,25),
        array(16,13)
        );
    $min_distance = sqrt(pow(($dots[0][0]-$dots[1][0]),2)+pow(($dots[0][1]-$dots[1][1]),2));
    $min_i = 0;
    $min_j = 1;
    for  ($i = 0; $i< count($dots)-1; $i++){
        for ($j = $i+1; $j < count($dots); $j++) {
            $cur_distance = sqrt(pow(($dots[$i][0]-$dots[$j][0]),2)+pow(($dots[$i][1]-$dots[$j][1]),2));
            echo "Сравниваем точки №$i и №$j.";
            echo "Расстояние между точками $i и $j = $cur_distance\n";
            if ($cur_distance < $min_distance) {$min_distance = $cur_distance;$min_i = $i;$min_j = $j;}
        }
    }
    echo "Наименьшее расстояние между точками $min_i и $min_j - $min_distance";
?>