PHP Upload Script

I wrote a simple php script, which allows user to upload a file to the server. It works, but I'm not very sure about security. Could you give me some hints about security mistakes?

In a nutshell: User uploads a file from form.html, then a file is saved in uploads/ directory on the server, and a direct link to it is recorded in a database. Then that link is presented to the user, so he is able to download the file. The execution of that file is forbidden using .htaccess.

form.html

<div id="quickFileSubmit" style="margin-left: 20px; display: none">
    <table>
        <tr>
            <td>
                <form enctype="multipart/form-data" class="smallForm"
                      action="action.php?act=quickFileSubmit" method="post"
                      style="margin-top: 5px;">
                    <label style="font-size: 12px;">File:</label>
                    <input type="file" name="uploadfile" readonly="true" size="30"/>
                    <input type="submit" value="Submit" />
                </form>
            </td>
            <td style="width: 100%;"></td>
        </tr>
    </table>
</div>

action.php

//some actions

else if ($_REQUEST["act"] == "quickFileSubmit") {
    $basename = getUploadBasename();
    uploadFile();
    header("location:index.php");
}

function uploadFile() {

    if (strlen($_FILES['uploadfile']["name"]) > 0) {
        $target_path = "uploads/";
        $basename = basename( $_FILES['uploadfile']['name']);
        $target_path = $target_path . $basename;
        if (encode($basename) == $basename) {
            if(move_uploaded_file($_FILES['uploadfile']['tmp_name'], $target_path)) {

                // here goes saving of file info

                return $basename;
            } else{
                // upload failed.
                echo "File upload failed.";
                return null;
            }
        } else {
            echo "Illegal characters in file name.";
            return null;
        }
    }
}

Also, I have put .htaccess in the uploads dir:

.htaccess

SetHandler default-handler
Options -Indexes