php4/php5 plugin

I have a plugin that i developed on my php5 webserver. Now some folks are trying it out finding issues that I can’t reproduce, I suspect the issue is the plugin running on a php4 web server.

Is there a tool that I can run on my code to find out if it is php4 compliant? I downgraded my server to php4 temporarily, but ran into some database issues so i couldn’t get wordpress to run.