This extension is a PHP binding for Google LevelDB Formula was removed
Last versions were
php56-leveldb requires the following formulae to be installed:
autoconf 2.69 Automatic configure script builder
leveldb 1.20_2 Key-value storage library with ordered mapping

Recent formula history

ilovezfs php56: migrate to homebrew/core (#4835)
ilovezfs php56-leveldb: bottle revision to rebuild.
Andreas Braun Add description for leveldb formula
Andy Blyler fix style issues
Andy Blyler php56-leveldb: convert from sha1 to sha256

Formula code at GitHub