php submit action

<html>
 <head>
  <title>PHP Test</title>
 </head>
 <body>
 <?php echo '<p>Hello World</p>'; ?>
 <h3>

<?php
$output = shell_exec('ls -lart');
echo "<pre>$output</pre>";
?>


m: <input type="text" name="m" value="<?php echo $m;?>">
<br>
<br>
gamma: <input type="text" name="gamma" value="<?php echo $gamma;?>">
<br>
<br>
epsilon: <input type="text" name="epsilon" value="<?php echo $epsilon;?>">
<br>
<br>
<!--Comment: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea> -->



<input type="submit" name="submit" value="Submit">

</h3>
 </body>
</html>