sleep_and_wakeup.md

Sleep and wakeup

There is one special feature with saving objects, though, and that is the fact that when serialize() and unserialize() are called, they will look for a __sleep() and __wakeup() function on the object they are working with respectively. These functions, which you have to provide yourself if you want them to do anything, allow you to properly keep an object working during its hibernation period (when it is just a string of data)

For example, when __sleep() is called, a logging object should save and close the file it was writing to, and when __wakeup() is called the object should reopen the file and carry on writing. Although __wakeup() need not return any value, __sleep() must return an array of the values you wish to have saved. If no __sleep() function is present, PHP will automatically save all variables, but you can mimic this behaviour in code by using the get_object_vars() function

If you find yourself needing to save objects, keep __sleep() and __wakeup() in mind - together they allow you to keep objects fully working across pages

class logger {
    private function __sleep() {
        // do stuff here
        return array_keys(get_object_vars($this)); // get_object_vars() takes an object as its only parameter, and returns an array of all the variables and their values in the object

        // You need to pass the variables to save back as the values in the array, so you should use the array_keys() function on the return value of get_object_vars()
    }

    private function __wakeup() {
        $this->openAndStart();
    }

    private function saveAndExit() {
        // ...[snip]...
    }
}