Tracing object instance creation / duplication

wisskid

I'm wondering if there is any way to systematically trace object instance creation / duplication throughout a PHP script:

Over the past year, I worked on a Content Management System in PHP. It is Object Oriented, I used references where appropriate to avoid an enormous duplication of objects and made sure the different Classes staid as lightweight as possible.

After I started including code interacting with database objects in classes that inhertied from the "Paragraph" class, I found out that some objects where created several times. Image adding a "counter" element to a page to find that it counts 4 hits for each page visit... 😕

By now, I think I traced most coding errors (missing &'s and so on) and it seems to be working fine. :rolleyes: Nevertheless, I am not totally confident that I traced all errors and imagine that this would be a structural problem.

ahundiak

The good news is that php 5 should make using references a thing of the past. Or at least not as error prone.

There is no standard way to determine if two references point to the same object. This article provides a work around:
http://www.digiways.com/articles/php/smartcompare/

You basically create a new member variable in one object then test to see if it exists in another object. As a variation, you could actually just build in a member variable, change the value in one object and then test to see if it changed in the other object.

Trying to apply this to an existing program might not be real easy. If you always use a factory function to create new classes then the function could store the references in some sort of global array. You could then test a given variable to see if it's in the array or not. Kind of messy but possibly good for debugging.

wisskid

Yes, I was afraid something like that would be the only solution. I guess i'll wait till my hosting provider installs PHP5 then.

Not a whole lot of fun to retrace all my PHP4 code to find all assignments of objects and then add assertions, changing dummy variables and all.

As I understand it, PHP5 will reference objects by default and use methods such as ->__clone() to copy objects, which will make the whole thing much more transparent. 🙂

HalfaBee

Would a var_dump( $GLOBAL ) show the obvious cross references?

HalfaBee