Dirty Mixed PHP7 & PHP8

demo-7x8x-mixed.php

<?php
declare(strict_types=1);

/**
 * PHP8
 *  add : https://php.watch/versions/8.0/union-types
 */

class SimpleMath
{
    #[PHP8] private int|float $inline_num; /*
    private $inline_num; /* PHP<8 */

    #[PHP8] public function setNum(int|float $num=8): void { /*
    public function setNum($num=7): void { /* PHP<8 */
        $this->inline_num = $num;
    }

    #[PHP8] public function squareAndAdd(int|float $num): int|float { /*
    public function squareAndAdd($num) { /* PHP<8 */
        return $num ** 2 + $this->inline_num;
    }
}

$simple = new SimpleMath();

$simple->setNum();

echo $simple->squareAndAdd(1.2) . PHP_EOL;