I want to build a web game with Blender and I know PHP. Is it possible to mesh Blender with PHP?
As @Byte56 mentions you could create graphics in Blender and then export them.
But, as @Bane and @stephelton mention, you appear to have some holes in your knowledge of game development, and possibly development generally.
I would recommend you take a look at How do I make games? A Path to Game Development and even some other questions here or on related SE's like:
Of course it is possible. You can use urllib and open a http connection from the python, get data from PHP and visualize in Blender. You can even do this online using Burster Burster website.
The second possibility, depending on what you realy want to do. If you want in example to do some modification of camera using the web, and you want to get a rendered image from Blender over the Web you can implement very simple WWW server in Python in Blender (example here: making a simple web server in python).
So, if you can describe your task in more details, i would be able to answer with examples of how to do this .
If you know PHP you also know that PHP is a server-side scripting language which in turn needs another language (html, html5 for instance) to display something.
So if we consider your question as: "Is it possible to combine Blender with html/html5?", then the answer is yes you somehow can do it..
Another solution to "combine" Blender with you browser content, is to simply export images from Blender and use then with html...
Next, you can use 3D plug-ins such as UNITY but it's already far from your "PHP" question ;)