是否有可能在php中序列化SplEnum

Question

Is it possible serialize SplEnum? I'm trying use SplEnum, but userialized instance has only default value. For example:

class Test extends SplEnum
{
    const __default = self::A;
    const A = 1;
    const B = 2;
}

...

$t = new Test( Test::B );
$s = serialize($t);
$t2 = unserialize($s);

Variable $t2 is instance of Test but with default value.

Answer 1

The reason why you don't get an expected value after unserialize is that SplEnum is not just a regualar PHP class. It is a kind of hack. The value is kept in its own structure, not in PHP object itself as you can see here

https://github.com/davidcoallier/SPL_Types/blob/master/spl_type.c in method spl_type_object_new_ex

They create an internal structure "object"

object = emalloc(sizeof(spl_type_object));

that holds the value

ZVAL_ZVAL(object->value, *def, 1, 0);

The unserialize function does not know a thing about this internal object and cannot change its value. Hence this peculiar behaviour.

Update

You might want to use casting in order to preserve the object's value. In your case it could have been:

$casted_value = (int) $t;

At least an integer is easier to handle.

Update 2

A working example with working serialization.

class Test2 extends SplEnum  implements Serializable 
{
    const __default = 1;
    const A = 1;
    const B = 27;
    const C = 31;

    public function serialize() {
            return serialize ((int) $this);
    }

    public function unserialize($serialized) {
        $this->__construct (unserialize($serialized));
    }
}