<table>
<tr>
<td>
<form method='post' action='?='>
<textarea name='encode' cols='20' rows='20'>
<?php
$data =  (htmlentities(isset($_POST['encode']) ?  $_POST['encode'] : "" ));
echo base64_encode($data);
?>
</textarea>
</td>
<br>
<td>
<input type='submit'>
</td>
</form>
</tr>

<tr>
<td>
<form method='post' action='?='>
<textarea name='decode' value='Decode Box' cols='20' rows='20'>
<?php
$data2 =  (htmlentities(isset($_POST['decode']) ?  $_POST['decode'] : "" ));
echo base64_decode($data2);
?>
</textarea>
<br>
</td>
<td>
<input type='submit'>
</td>
</tr>
</form>
</table>