Untitled

<?php
if(isset($_POST['cm']))
{
   if(!is_numeric($_POST['cm']))
   {
      $error = 'Is not a number!';
   }
   else
   {
      $m = $_POST['cm'] / 100;
   }
}
?>
<!doctype html>
<html>
   <head>
      <title>Centimeters to meters converter</title>
      <style type="text/css">
      .error {
      color: #f00;
      }
      </style>
   </head>

   <body>
      <form method="POST">
         <label for="cm">Centimeters</label>
         <input type="text" id="cm" name="cm" value="<?php if(isset($m)){echo $_POST['cm'];} ?>" size="5" />
         <button type="submit">Convert</button>
      </form>
<?php
if(isset($error))
{
   echo "      <span class=\"error\">{$error}</span>\n";
}
elseif(isset($m))
{
   echo "      There are <strong>{$m}</strong> meters to <strong>{$_POST['cm']}</strong> centimeters\n";
}
?>
   </body>
</html>