Php jquery表单插件将重复条目保存到mysql表

我正在为一个朋友网站设计一个管理面板。我正在使用jquery表单插件提交表单，而不刷新页面。由于此表单需要将图像上载到服务器，因此我无法使用我更熟悉的ajax

这是我的表单/jquery：

    <script type="text/javascript" src="jquery.form.js"></script>

    <script type="text/javascript" >
     $(document).ready(function() { 

                $('#submitform').live('click', function()           { 
                           $("#preview").html('');
                    $("#preview").html('<img src="loader.gif" alt="Processing...."/>');
                $("#imageform").ajaxForm({
                            target: '#preview'
            }).submit();

                });
            }); 
    </script>

<form id="imageform" method="post" enctype="multipart/form-data" action='pages/addprodprocess.php'>
<table width="100%">
<tr>
<td>Product Name:</td> <td><input type="text" name="prodname" id="prodname" placeholder="Product Name"/></td>
</tr>
<tr>
<td>Product Description:</td> <td><textarea name="proddesc" id="proddesc" placeholder="Product Description"></textarea></td>
</tr>
<tr>
<td>Product Price:</td> <td><input type="text" name="prodprice" id="prodprice" placeholder="Price eg. 7.99"/></td>
</tr>
<tr>
<td>Product Category:</td> <td>
<?php
   $getcats = mysql_query("select * from product_cats");
    if(mysql_num_rows($getcats) == 0){
    echo '<select id="prodcat" name="prodcat" disabled="disabled">';
           echo '<option>Please create a category first!</option>';
           echo '</select>';
           }else{ 
           echo '<select id="prodcat" name="prodcat">';
   while($cats = mysql_fetch_array($getcats)){
   echo '<option value="'.$cats['cat_id'].'">'.$cats['cat_name'].'</option>';
   }
   echo ' </select>';

   }
   ?></td>
</tr>
<tr>
<td>Product image:</td> <td><input type="file" name="photoimg" id="photoimg" /></td>
</tr>

<tr><td></td><td><input type="submit" value="submit" id="submitform"/></td></tr>
</table>
</form>
<div id='preview'>
</div>

我的表单/jquery似乎工作正常，问题是在提交时处理表单。 提交时，它会被发送到我的“addprodprocess.php”页面进行处理，处理效果很好，但在将表单值保存到mysql时，它会将重复的相同数据多次保存到表中

这是我的处理页面：

<?php
$link2 = mysql_connect('localhost', 'username', 'pass'); 
if (!$link2) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('database'); 

//ADD PRODUCT
if (isset($_FILES['photoimg'])) {
$path = "../products/";
       $valid_formats = array("jpg", "png", "gif", "bmp");
    if(isset($_POST) && $_SERVER['REQUEST_METHOD'] == "POST")
        {
            $name = $_FILES['photoimg']['name'];
            $size = $_FILES['photoimg']['size'];

            if(strlen($name) && strlen($_POST['prodname']) && strlen($_POST['proddesc']) && strlen($_POST['prodprice']) && strlen($_POST['prodcat']))
                {
                    list($txt, $ext) = explode(".", $name);
                    if(in_array($ext,$valid_formats))
                    {
                    if($size<(1024*1024))
                        {
                            $actual_image_name = time().substr(str_replace(" ", "_", $txt), 5).".".$ext;
                            $tmp = $_FILES['photoimg']['tmp_name'];
                            if(move_uploaded_file($tmp, $path.$name))
                                {
                                mysql_query("INSERT INTO `products` (`product_name`,`product_desc`,`product_img`,`product_price`,`product_cat`) VALUES('".$_POST['prodname']."','".$_POST['proddesc']."','".$name."','".$_POST['prodprice']."','".$_POST['prodcat']."')");

                                    echo "<img src='products/".$name."'  class='preview' height='75' width='75'>";
                                }
                            else{
                                echo "failed";
                                }
                        }
                        else{
                        echo "Image file size max 1 MB";
                        }                   
                        }
                        else{
                        echo "Invalid file format..";   
                        }
                }

            else{
                echo "All fields MUST be filled in!";
                }

            exit;
        }
        }  
        ?>      

---

任何能帮助我的人，都将不胜感激

在插入之前，运行SELECT并确保它返回NULL