I was asked this interview question recently and I didn't know about this:
"Which PHP functions can be used to customize the serialization process of an object?"
Any sample implementation will be of great help to understand.
Clearly described in official documentation for Serializable interace - serialize and unserialize are the ones: http://php.net/manual/en/class.serializable.php
The old way is to implement methods __sleep and __wakeup which were supposed to remove references to runtime resources and reinitialize them respectively. This is not supported if the class implements Serializable mentioned earlier.