<?php


use PHPUnit\Framework\TestCase;

class TestLanguage extends TestCase
{
    public function testYield()
    {
        $checker = function ($val) {
          return $val > 5 ? true : false;
        };

        $map_adder = function ($datas,$delta)
        {
            foreach ($datas as $val) {
                $k = yield $val + $delta;
            }
        };

        $datas = [1,2,3,4,5,6];
        $x = $map_adder($datas,2);

        foreach ($x as $v) {
            $t = $checker($v);
        }
    }

    public function testStrtolow()
    {
        $val = '';
        $val = null;
        $k = strtolower($val ?? '');
    }
}