title: group array elements respect to the values of another array
body: <p>I know it's a simple question, but I didn't succeed in finding the answer, yet...</p>
  
  <p>Which is the most effective way to group array elements respect to the values of another array in PHP? </p>
  
  <p>Example:  </p>
  
  <pre><code>names = [antonio, luigi, marco, stefano, gennaro, pino, lorenzo];
  surnames = [bianchi, rossi, rossi, brambilla, rossi, rossi, brambilla];
  </code></pre>
  
  <p>expected result:</p>
  
  <pre><code>bianchi:
  antonio
  
  rossi: 
  luigi, marco, gennaro, pino
  
  brambilla:
  stefano, lorenzo
  </code></pre>