Not having to wait fifteen minutes for your app to compile and link, for one thing. But seriously, the C++ implementation comes at the cost of many of PHP's features; a "more complex solution" would allow those features to be kept. And while C++ is fast, a script translated into C++ is not going to be as fast as if you had written the application directly in C++, unless the compiler is very, very smart. (I have not seen any implementation that does this; GHC's native code generator produces faster code than it's "via-C" code generator, for example.)
Also, static compilation precludes runtime-based optimization techniques, which has made a lot of code run "faster than C" (including C, ironically; see LLVM).
So anyway, all this is is a way to compile a limited subset of PHP to C++. In doing so, you have to write a special dialect of PHP, without PHP's easy deployability and code/test/debug cycle.
In that case, why are you using PHP to begin with, when a language like GHC or SBCL would run faster and without any compromises?
Not even the Linux kernel takes 15 minutes to compile and link anymore. My desktop machine does it in under 10 minutes, but I realize you weren't being entirely serious.
Also, static compilation precludes runtime-based optimization techniques, which has made a lot of code run "faster than C" (including C, ironically; see LLVM).
So anyway, all this is is a way to compile a limited subset of PHP to C++. In doing so, you have to write a special dialect of PHP, without PHP's easy deployability and code/test/debug cycle.
In that case, why are you using PHP to begin with, when a language like GHC or SBCL would run faster and without any compromises?