I have seen a product that claims to be able to interpret UML models and conert into PHP -never tried it, if you already are using a UML tool it could be of interest.
However its jsut a tool. Like anyt language there is a bit of a learning curve with PHP, it snot particularly steep. Like any language, providing you know what you want to say its a fairly mechanistic process to convert it to a computetr language like PHP. PHP is particularly cryptic, the debugging can be a bit odd / uniformative but it works fine. I'd suggest buying a vary basic book to take you through the first steps. There may even be a few on line tutorials which do the similar thing.
I think the first PHP books I bought were "PHP fast&easy web development by Julie Meloni, and PHP for the world wide web by Larry Ullman which gave a basic introduction, and since then have added PHP Bible & PHP5 as the need for more advanced topics arose.