Casting如何在PHP中运行？

$int = 123;
$float = 123.45;
$string = '123';

$int_cast = (int) $float; // 结果为 123
$float_cast = (float) $int; // 结果为 123.0
$string_cast = (string) $int; // 结果为 '123'

$float = 123.45;
$int = 123;
$string = '123.45';

$float_cast = (float) $int; // 结果为 123.0
$int_cast = (int) $float; // 结果为 123
$string_cast = (string) $float; // 结果为 '123.45'

$bool = true;
$int = 1;
$float = 1.0;
$string = 'true';

$bool_cast = (bool) $int; // 结果为 true
$int_cast = (int) $bool; // 结果为 1
$float_cast = (float) $bool; // 结果为 1.0
$string_cast = (string) $bool; // 结果为 '1'

$array = [1, 2, 3];
$string = '1,2,3';

$array_cast = (array) $string; // 结果为 ['1', '2', '3']
$string_cast = (string) implode(',', $array); // 结果为 '1,2,3'

class Example {
    public $property = 'value';
}

$object = new Example();
$string = '{"property":"value"}';

$object_cast = (object) json_decode($string, true); // 结果为 Example 对象
$string_cast = (string) json_encode($object); // 结果为 '{"property":"value"}'

$null = null;
$string = 'null';

$null_cast = (unset) $string; // 结果为 null
$string_cast = (string) null; // 结果为 ''