Finding call-time pass by references in PHP.

While trying to move an older code base to a newer system and thus a newer version of PHP (5.3 -> 5.5), I knew that some of the code would need to be changed to avoid using some removed features. Specifically, I mean call-time pass by references. For those who don’t know, this is kind of a weird feature of earlier versions of PHP that allows one to call a function and pass any of the arguments by reference rather than the usual call by value if the caller prepends an argument variable with the “reference to” operator &.

So, to illustrate, normally this code won’t have side effects because of call by value:

However there will be side effects if the caller chooses pass by reference:

I thought a regex might be in order to find these guys and fix them:

but it was a naive idea, and this regex devolved (heh) to its current form before I realized I could just use the built-in linter to find the problem spots.