Creates a polygon SVG with n vertices and a top apex

polygon-svg.php

<?php

// Author : sfaut <https://github.com/sfaut>
// Publication date : 2022-09-06

// Usage :
// <img src="polygon-svg.php?vertices=5" alt="A SVG pentagon!">

$vertices = (int)$_GET['vertices'] ?? 5;

$start = 3 * M_PI / 2; // Apex en haut, pas M_PI / 2 car coordonnées SVG (-1, -1) en haut à gauche
$angle = $start;
$points = [];
for ($i = 0; $i < $vertices; $i++) {
    $points[] = [cos($angle), sin($angle)];
    $angle += (2 * M_PI) / $vertices;
}

$points = implode(' ', array_map(fn ($p) => implode(',', $p), $points));

header('Content-Type: image/svg+xml');

?>
<?xml version="1.1" standalone="yes"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" height="500" width="500" viewBox="-1 -1 2 2">
    <polygon points="<?= $points ?>"/>
</svg>