local IP script question

I assume this would be easy to accomplish, but I can't seem to figure it out.. I'm running Apache/PHP on my machine (WinXP Pro).. I want to create a local php script that detects my ISP's assigned IP address and add a port to it (e.g.: http://xxx.xxx.xxx.xxx:xxxx ).. I often am running SpyAmp (a WinAmp plugin) and that creates a basic html output page using a different port than Apache does.. They both run together fine without conflicts, but I can't figure out how to create a php script that finds my IP address and adds my SpyAmp assigned port to it.. I don't want to have to manually get my IP thru "run --> cmd /k ipconfig" each time as I'd like to bookmark the local php page instead.. Is this possible using REMOTE_ADDR somehow? If so, what function(s) do I need to look into and how would I configure this? Does the script need to find my IP, then forward me to another page using the header() function adding the port to my IP? If you have a working example, tips or a URL to help me on my way, I'd appreciate it.. TIA.. Take care.. peace.. eriol