On my Windows machine I also use ST2, but it handles autocomplete of existing variable names in the current file. How do I enable this in ST2 on my mac? Syntax is PHP
If you have Package Control installed, there's probably a particular package that's causing the issue.
Check your installed packages by pressing CtrlShiftP (or CmdShiftP on a Mac) and typing
You could then, for example, remove offending packages (by typing