$num = 123;
$str = strval($num);
echo gettype($str); // 输出 string
$bool = true;
$str = strval($bool);
echo gettype($str); // 输出 string
$array = array('a', 'b', 'c');
$str = strval($array);
echo $str; // 输出 Array
$null = null;
$str = strval($null);
echo gettype($str); // 输出 string
$num = 123;
$str = 'The number is ' . strval($num);
echo $str; // 输出 The number is 123
