join_path.php

<?php

/**
 * @param string ...$rest
 */
function join_path(...$rest): string
{
    if (count($rest) === 0) {
        return '';
    }

    if (count($rest) === 1) {
        return $rest[0];
    }

    $head = array_shift($rest);
    $head = $head === '/' ? $head : rtrim($head, '/');

    $tail = join_path(...$rest);

    return $tail ? rtrim($head, '/') . '/' . ltrim($tail, '/') : $head;
}