<form method="post">
<textarea name="opisanie" cols="10" rows="15"><textarea>
<input type="submit" name="send" value="Promeni">
</form>
<?php
if($_POST['send']){
$text = $_POST['opisanie'];
$query = "UPDATE tablica SET opisanie='$text' WHERE userid='$userid'";
$query_m = mysql_query($query) or die('ne uspeshno');
}
?>