string to numeric coercion

Dear comrade,

I couldn't help but notice your library doesn't implement this _completely sensible coercion_ of strings to numbers:

    Prelude.PHP> "1 orange" + "2 bananas"
    "3"

I hope you can understand my outrage regarding this deficiency — as such, I have taken it into my own hands and, in the spirit of open source, contribute this patch to your library to further the glowing combined efforts of both the PHP and Haskell communities.

Good day to you, sir.