Update: The developers of MAMP recommend the following workaround:
Workaround for the 10.10 Preview 5 bug: Rename the file “envvars” located in into “_envvars”
If you’re running MAMP Pro 3 and you installed Yosemite preview 5, you’ve probably noticed Apache won’t start anymore, with the following error:
dyld: Symbol not found: _iconv
Referenced from: /usr/lib/libmecabra.dylib
Expected in: /Applications/MAMP/Library/lib/libiconv.2.dylib
This is some kind of library error because of an updated library in the newest preview. You can fix this by forcing your own version of libiconv onto your computer, though you have to replace the system default version of libiconv, which in theory could cause bad things to happen – i’ve not noticed anything, but your milage will vary – and you should make sure you’ve got a system backup of everything incase the worst does happen.
Hopefully you’ve already got homebrew installed – if not, grab it from brew.sh and follow those instructions, then:
1) Allow homebrew to install duplicates of system software:
brew tap homebrew/dupes
2) Install libiconv:
brew install libiconv
3) Force it to link (replace) the system default:
brew link libiconv --force
4) Delete the MAMP version of libiconv:
Then everything should start properly.