title: How to add smart contract functionality in PHP?
body: <p>I'm working on project with main theme - sales.
  So, for front end (React) and Backend(PHP).</p>
  
  <p>I had a problem understanding how to use my smart contract in the project.
  For deploy i use ethereum wallet 0.9.0 and test network Rinkeby. In EW he is working.</p>
  
  <p>Let's pretend that I have button buy in my code, and, i have function in my contract like:</p>
  
  <pre><code>function Buy() 
      public 
      payable 
  {
      require (msg.sender != seller);
      require (msg.value &gt;= price);
      orderNum++;
      safePay +=msg.value;
  }
  </code></pre>
  
  <p>Now, how i can use it? 
  I heard about web3.js, but (i'm not sure) i need php requests for this. </p>
  
  <p>Or, if my contract deploy in ethereum-wallet Rinkeby i can use it straight from just code and don't need deploy again. </p>
  
  <p>I'm beginner in this theme and can do mistake (even in the view), but will be very glad, if someone can explain this.</p>
  
  <p>Thanks.</p>