The main source of information about PHP for all developers is the official website
http://php.net. On its pages you can find the section of the documentation, including in Russian.
Unfortunately, translation into many languages is not always complete and lags behind the English version. We will not be able to highlight on these pages all the possibilities of the language, we simply will not have enough time and space for this, so you will have to refer to the PHP documentation in order to use all the PHP capabilities.