<?php

// your code goes here
echo "!!'true'  : " . (!!'true'  ? "true" : "false") . PHP_EOL;
echo "!!'false' : " . (!!'false' ? "true" : "false") . PHP_EOL;
echo "!!'null'  : " . (!!'null'  ? "true" : "false") . PHP_EOL;
echo "!!null    : " . (!!null    ? "true" : "false") . PHP_EOL;

echo "(bool)'true'  : " . ((bool)'true'  ? "true" : "false") . PHP_EOL;
echo "(bool)'false' : " . ((bool)'false' ? "true" : "false") . PHP_EOL;
echo "(bool)'null'  : " . ((bool)'null'  ? "true" : "false") . PHP_EOL;
echo "(bool)null    : " . ((bool)null    ? "true" : "false") . PHP_EOL;