Hi,
I'm an experienced full stack web developer. I have implemented many sites using PHP (Zend Framework, CodeIgniter), Javascript (raw, jQuery, jQuery mobile, angularJS) and CSS.
I also have abilities on Java (Spring and Java ServerFaces).
I would like to know details about the site that you're considering to change and which will be the time to execute the project.
As I understand from your post you need web services on PHP to be consumed by Java Application that has to be designed? Do you have an estimated completion time requirement?