There are four different points on a plane, P(xp,yp), Q(xq, yq), R(xr, yr) and S(xs, ys)

<?php
define('EPS', 1e-8);
    $a = fscanf(STDIN, '%f %f %f %f %f %f %f %f');
    $line = array();
    $line[] = $a[1] - $a[3] === 0.0 ? INF : ($a[0] - $a[2]) / ($a[1] - $a[3]);
    $line[] = $a[5] - $a[7] === 0.0 ? INF : ($a[4] - $a[6]) / ($a[5] - $a[7]);
    if (max($line) === INF && min($line) === 0 || abs($line[0] * $line[1] + 1.0) < EPS) {
        echo 'Orthogonal';
    } else {
        echo 'Not orthogonal';
    }
    echo PHP_EOL;
?>