I've found a new promising project in early beta stage: phc - the open-source PHP compiler.

phc is an open source compiler for PHP with support for plugins. In addition, it can be used to pretty-print or obfuscate PHP code, as a framework for developing applications that process PHP scripts, or to convert PHP into XML and back, enabling processing of PHP scripts using XML tools.

phc for PHP programmers:

* Compile PHP source into an (optimized) executable.
* Compile a web application into an (optimized) extension.
* Pretty-print PHP code.
* Obfuscate PHP code.
* Combine many php scripts into a single file.
* Optimize PHP code using classical compiler optimizations.

phc for tools developers:

* Analyse, modify or refactor PHP scripts using C++ plugins.
* Convert PHP into a well-defined XML format, process it with your own tools, and convert it back to PHP.
* Operate on ASTs, simplified ASTs, or 3-address code.
* Analyse or optimize PHP code using an SSA-based IR.

Link: phc