Getting the text undefined added to the end of post in textarea when submitting form

Question

I'm a beginner in php so there might be alot wrong with this code but I really need some help!

I'm making an textarea for users to post to users walls. Everything works fine and the form is submitting to the database the only thing that goes wrong is that the text line undefined get added to the end of the input text both in the textarea and in the database. I most have forgotten to assign something but what?

my html code:

<form action="" method="POST">
    <textarea id="message" name="pinlagg" rows="4" placeholder="Inlägg:"onfocus="this.placeholder = ''" onblur="this.placeholder = 'Inlägg:'" ></textarea>
    <input type="submit" class="button" value="Skicka"/>
</form>

my php code:

if (isset($_POST['pinlagg'])) {
$session_user_id = $_SESSION['id'];
$username = $user_data['userName'];
$pinlagg = $_POST['pinlagg'];
$mysql['pinlagg'] = mysql_real_escape_string($clean['pinlagg']);

$sql="INSERT INTO profile_post(post, username, added) VALUES('$pinlagg', '$username', '".date("Y-m-d H:i:s")."')";
mysql_query($sql);
} else {
    echo 'Du har inte skrivit något!';
}

My database has 4 columns. id, post(varchar), username(varchar) and added(timestamp).

I also have a problem with getting the local time from timestamp.

js for including emojis:

$(document).ready(function(){

$('.button').click(function(){

    var smiley = $(this).attr('smiley');
    var message = jQuery.trim($('#message').val());

    if (message == '') {
        var sp = '';
    } else {
        var sp = ' ';
    }

    $('#message').focus().val(jQuery.trim(message + sp + smiley + sp))
});
    $('#message').keyup(function(e){
    if (e.keyCode == 13) {
        var message = $(this).val();

        $.post('replace.php', {message: message}, function(data){
            $('#display_message').append(data + '<br/><br/>');
        });
    }
});
});

php for including emojis:

<?php
$message = $_POST['message'];

$message = str_replace(':)', '<img src=./emoji/glad_face.png', $message);
$message = str_replace('%D', '<img src=./emoji/drunk_face.png', $message);
$message = str_replace(';)', '<img src=./emoji/winky_face.gif', $message);
$message = str_replace(';P', '<img src=./emoji/ha_face.gif', $message);
$message = str_replace(':(', '<img src=./emoji/sad_face.png', $message);
$message = str_replace('X(', '<img src=./emoji/offended_anim.gif', $message);
$message = str_replace(';(', '<img src=./emoji/crying_anim.gif', $message);
$message = str_replace(':/', '<img src=./emoji/wtf_face.png', $message);
$message = str_replace(':r', '<img src=./emoji/rant_face.gif', $message);
$message = str_replace(':o', '<img src=./emoji/ohno_face.png', $message);
$message = str_replace('<3', '<img src=./emoji/love.png', $message);
$message = str_replace('<}3', '<img src=./emoji/broken.png', $message);
$message = str_replace('(Y)', '<img src=./emoji/like.png', $message);
$message = str_replace('(N)', '<img src=./emoji/dislike.png', $message);
$message = str_replace('}-', '<img src=./emoji/fu.png', $message);
$message = str_replace(':x', '<img src=./emoji/kiss_anim.png', $message);

echo $message;
?>