Is it possible to dynamically reload PHP code while script is running?

Question

I'm having a multiplayer server that's using PHPSockets, and thus is written entirely in PHP.

Currently, whenever I'm making any changes to the PHP server-script I have to kill the script and then start it over again. This means that any users online is disconnected (normally not a problem because there aren't so many at the moment).

Now I am rewriting the server-script to use custom PHP classes and sorten things up a little bit (you don't want to know how nasty it looks today). Today I was thinking: "Shouldn't it be possible to make changes to the php source without having to restart the whole script?".

For example, I'm planning on having a main.php file that is including user.php which contains the class MyUser and game.php which contains the class MyGame. Now let's say that I would like to make a change to user.php and "reload" the server so that the changes to user.php goes into effect, without disconnecting any online users?

I tried to find other questions that answered this, the closest I got is this question: Modifying a running script and having it reload without killing it (php) , which however doesn't seem to solve the disconnection of online users.

UPDATE

My own solutions to this were:

1. At special occations, include the file external.php, which can access a few variables and use them however it'd like. When doing this, I had to make sure that there were no errors in the code as the whole server would crash if I tried accessing a method that did not exist.
2. Rewrite the whole thing to Java, which gave me the possibility of adding a plugin system using dynamic class reloading. Works like a charm. Bye bye PHP.

Answer 1

Shouldn't it be possible to make changes to the php source without having to restart the whole script?

[...]

I'm planning on having a main.php file that is including user.php which contains the class MyUser

In your case, you can't. Classes can only be defined once within a running script. You would need to restart the script to have those classes redefined.

Answer 2

I am not too familiar with PHP but I would assume that a process is created to run the script, in doing so it copies the instructions needed to run the program and begins execution on the CPU, during this, if you were to "update" the instructions, you'd need to kill the process ultimate and restart it. Includes are a fancy way of linking your classes and files together but ultimately the processor will have that information separate from where the file of them are stored and it is ultimately different until you restart the process.

I do not know of any system in which you can create code and actively edit it and see the changes while that code is being run. Most active programs require restart to reload new source code.

Answer 3

Runkit will allow you to add, remove, and redefine methods (among other things) at runtime. While you cannot change the defined properties of a class or its existing instances, it would allow you to change the behavior of those objects.

I don't recommend this as a permanent solution, but it might be useful during development. Eventually you'll want to store the game state to files, a database, Memcache, etc.