Enter til at køre en form

Har søgt og søgt og prøvet en masse.... men kan ikke få enter til at virke med min form den poster ikke indholdet når jeg trykker på enter den loder bare siden igen ?


Form :

    <form id="search" action="sf2.php" method="post">
    <input type="text" name="search" size="30">
    <input type="submit" name="submit" value="Søg" />
    </form>


Hele koden:

if(isset($_POST['submit'])){ //if the form was submited
    $search = $_POST['search']; //put in $search what the user entered
    if(trim($search) == ''){ //if the user didn't type a keyword
        $errors = '<font color="red">Du skal indtaste din søgning</font><br /><br />';
    }
    if($errors == ''){ //if we don't have any errors
                      // $search holds what the user typed
        $query = "SELECT * from news WHERE title LIKE '%$search%' OR post LIKE '%$search%' OR author LIKE '%$search%'";
        $result = mysql_query($query) or die(mysql_error());
        if($result){
            display_form();//redisplay the search box
            echo "<h1>Søgeresultat fandt ". mysql_num_rows($result)." hits </h1><br />";
            echo "<ul>";
            while ($row = mysql_fetch_array($result, MYSQL_ASSOC)){
                $mess=$row['post'];
                //$view = "forum/setopic.php?id=".row['id'];
                echo "<li><a href=forum/setopic.php?id=".$row['id'].">".$row['title'].'</a></li>';
                echo '<p style="margin-right:100px;margin-top: 0px;">'.snippet($mess, 200, true).'</p>';//bring only 200 chars from datatabase
            }
        }
    }
}

if(!isset($_POST['submit']) || $errors != '?????'){
  echo $errors;
  display_form();//display first time the search box
}


function display_form(){
    ?>
    <form id="search" action="sf2.php" method="post">

    <input type="text" name="search" size="30">
    <input type="submit" name="submit" value="Søg" />
    </form>
    <?php
    } 
function snippet($text, $chars, $dots = false)
    {
        $end_char = substr($text, $chars, 1);
        if(preg_match('#S#', $end_char))
        {
            $chars += strpos($text, ' ', $chars) - $chars;
        }
        $ret = ($dots) ? substr($text, 0, $chars) . '...' : substr($text, 0, $chars);
        return $ret ;
    }