title: $_POST checking empty
body: <p>I need a function which can check my <code>$_POST</code> array, for example see this code, there is nothing common in the <code>$_POST</code> array. But i want to check if the array is returning null value from the user.</p>
  
  <pre><code>&lt;?php
  switch ($_GET['action']) {
    case "one":
    $a=$_POST['a'];
    echo "your value is". $a;
    break;
  
    case "two":
    $b=$_POST['b'];
    $c=$_POST['c'];
    echo "your value is". $b."--".$c;
    break;
  
    case "three":
    $x=$_POST['x'];
    $y=$_POST['y'];
    $z=$_POST['z'];
    echo "your value is". $x."--".$y."--".$z;
    break;   
  }
  ?&gt;
  </code></pre>