Formulario simple para encriptar (md5, base64, urlencode, sha256)

<?php

function sha256($t){
    return hash('sha256', $t);
}

$functions = array(
    'md5',
    'base64_encode',
    'urlencode',
    'sha256'
);

if($_POST['t'])
    echo '<textarea class="tA">'.$functions[$_POST['f']]($_POST['t']).'</textarea><br><br>'
;

?>
<style>
   .tA{
      width:400px;
      height:200px
   }
</style>

<form method="post">
    <textarea name="t" class="tA"></textarea><br>
    <select name="f">
<?php
        foreach($functions AS $k=>$t)
            echo "<option value=$k>$t</option>"
        ;
?>
    </select>
    <input type="submit" value="Encriptar">
</form>