title: PHP is_nan function: Notice: A non well formed numeric value encountered
body: <p><br>
  I want to check of there is a ean code (only numeric) in the $_GET method. And of check of that is a number. When it is not of that two i want to redirect to another page, and exit the php script.</p>
  
  <pre><code>if(!isset($_GET["ean"])){
      header('Location: /products.php');  
      exit();
  }else{
      if(is_nan($_GET["ean"])){
          header('Location: /products.php');
          exit();
      }
  }
  </code></pre>
  
  <p>When $_GET["ean"] = 234234sd (So, it is not numeric) there is a php error:<br>
  <code>Notice: A non well formed numeric value encountered in ..... on line 9</code><br>
  Line 9 is the line with de is_nan function.</p>
  
  <p>Thanks,</p>