<?php 
echo"<form action='' method='post'> 
    <input type='text' name='unos'>
    <input type='submit' value='Enkriptuj'> 
</form>";

if (isset($_POST['unos'])) { 
    $ep = md5(strip_tags($_POST['unos'])); 
    echo "Originalni text: <b>".$_POST['unos']."</b>
   </br>MD5: <b>$ep</b>";          
}
?>