You can find more information about how PHP executes in this article.
You could try HHVM which does compile it into bytecode which is then compiled using a JIT compiler (just like Java works).
Using HHVM can be a big upgrade IF you are willing to learn how to use it properly (don't ask me, I barely scraped the surface of it).
One of the major upsides of HHVM is that it compiles the code one, then reuses the same bytecode over and over again, which is massively faster than just interpreting.
However, PHP can just use OPcache to achieve pretty much the same.
It also does require more setup, and less code might work out-of-the-box.
So unless your app requires thousands if not millions of transactions per second and you're willing to rewrite code to work with HHVM, using HHVM might not be what you want (though it can be fun to look in none-the-less!).
For alternatives, your options are pretty much non-existent.
The power of PHP is that it doesn't have to be compiled.