title: Mathematical Operation PHP With time
body: <p>I'm traying to make a mathematical operation with php
  I have 2 variables, </p>
  
  <pre><code>$a2 = $info["Hora_final"]; //END TIME Example-&gt; 15:30:00
  $a1 = $info["Hora_inicial"];//FIRST TIME Example-&gt; 10:00:20
  
  But i want this operation (-) minus.
  $res = $a2 - $a1 ;
  echo $res;
  //output  5,30 Hours difference for example.
  </code></pre>
  
  <p>I try with this function but, is no like i want.</p>
  
  <pre><code> $a2 = $info["Hora_final"];
   $a1 = $info["Hora_inicial"];
  
  $h2h = date('H', strtotime($a2));
  $h2m = date('i', strtotime($a2));
  $h2s = date('s', strtotime($a2));
  $hora2 =$h2h." hour ". $h2m ." min ".$h2s ." second";
  
  $horas_sumadas= $a1." - ". $hora2;
  $text=date('H:i:s', strtotime($horas_sumadas)) ;
  </code></pre>
  
  <p>Thanks for you help ;)</p>