How does object serialize/unserialize work?

php object-serialization
dejjub-AIS picture dejjub-AIS · Oct 24, 2011 · Viewed 21.2k times · Source

I was reading about serialize/unserialize concepts of PHP. I was wondering how they are stored in the filesystem/db. I guess it is in the binary format. However, I wonder how entire class is stored? I understood that data in the data member can be stored but how are the methods stored?

I mean, how does PHP know what code is written inside the function of say, someFunc()?

$obj = new ClassName();
$obj->someFunc();
$serial = serialize($obj);
$unserialobj = unserialize($serial);
$unserialobj->someFunc();

PHP can know what to do at line #2, but how it know what to do at line #5 which is an unserialized object? Does it save the code as well?

Answer

deceze picture deceze · Oct 24, 2011

When serializing an object, PHP only stores the object's current state, i.e. its property values. It does not serialize its methods. The corresponding class needs to be loaded in memory at the time of unserialization. PHP will restore the state of the object from the serialized string and take the rest of the information (structure and methods) from the class of the same name.

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