PI SDK is announced for deprecation and we strongly discourage starting new development efforts against PI SDK.
You might be interested in earlier discussions on the subject and I believe this one is a pretty good starting point but you also could search the forums for the keyword PHP.
PHP is not a common programming language in the PI World which means you will not find much examples. Maybe it makes sense to take a step backwards. Can you indicate what your project is about?
If it has to be PHP, I suggest you to look at Developing a PHP application using PI Web API.
Please allow me to move your question to a sub space inside PI Developers Club ´for improved visibility.
Yes i know, but my client don't want to buy PIWebAPI. So i have to find a solution for sending datas to PI Server with PHP.
The only problem is to convert the PIValue to a variant with VT_VARIANT type.
I found no solution on internet to convert datas to a VT_VARIANT type variant on PHP.