请教php post 提交限制问题。

<?phpinclude("conn.php");if(isset($_POST['submit'])){ $sql="insert into dk_db(`id`,`dk_buy`,`dk_buy_value`,`dk_user`,`dk_oldyear`,`dk_pc`,`dk_set`,`dk_hometown`,`dk_phone`,`dk_message`,`dk_qita`,`dk_home`,`dk_jop`,`dk_transport`,`dk_function`)" .   "values('','$_POST[dk_buy]','$_POST[dk_buy_value]','$_POST[dk_user]','$_POST[dk_oldyear]','$_POST[dk_pc]','$_POST[dk_set]','$_POST[dk_hometown]','$_POST[dk_phone]','$_POST[dk_message]','$_POST[dk_qita]','$_POST[dk_home]','$_POST[dk_jop]','$_POST[dk_transport]','$_POST[dk_function]')"; mysql_query($sql); echo "发布成功";}?><form  action="daka2014.php" method="post"><h6 align="right"><input type="radio" name="dk_buy" <?php if (isset($dk_buy) && $dk_buy=="未成交") echo "checked";?>value="未成交" checked>未成交 <input type="radio" name="dk_buy" <?php if (isset($dk_buy) && $dk_buy=="已成交") echo "checked";?>value="已成交" >已成交  <input type="text" name="dk_buy_value" value="如未成交请说明。"/></h6><hr></hr><table cellspacing="1" bgcolor="#000000" width="950" align="center" cellpadding="1" ><tr bgcolor="#ffffff" align="center" height="30" > 	<td >客户名称</td>	<td colspan="2" ><input type="text" name="dk_user" value="" maxlength="8"/></td>	<td >年龄</td>	<td ><textarea name="dk_oldyear" cols="8" rows="1"></textarea></td>	<td rowspan="2">体貌特征</td>	<td colspan="4" rowspan="2"><textarea name="dk_pc" cols="55" rows="4"></textarea></td></tr><tr bgcolor="#ffffff" cellpadding="0" align="center" height="30" > 	<td >性别</td>	<td colspan="2" ><input type="radio" name="dk_set" <?php if (isset($dk_set) && $dk_set=="男" )echo "checked";?> 	value="男" checked>男 	<input type="radio" name="dk_set" <?php if (isset($dk_set) && $dk_set=="女") echo "checked";?> value="女"/>女</td>	<td >籍贯</td>	<td ><textarea name="dk_hometown" cols="8" rows="1"></textarea></td></tr><tr bgcolor="#ffffff" cellpadding="0" align="center" height="30">	<td>联系电话</td>	<td colspan="4" align="left"><input type="text" name="dk_phone" value="" maxlength="11" style="height:30px;width:300"/></td>	<td>信息来源</td>	<td align="left" colspan="4"><input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="介绍") echo "checked";?>	value="介绍" checked >介绍 <input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="大牌") echo "checked";?>	value="大牌">大牌<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="网络") echo "checked";?>	value="网络">网络<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="短信") echo "checked";?>	value="短信">短信<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="车身") echo "checked";?>	value="车身">车身<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="公交") echo "checked";?>	value="公交">公交<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="围挡") echo "checked";?>	value="围挡">围挡<br/><input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="路过") echo "checked";?>	value="路过">路过<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="报纸") echo "checked";?>	value="报纸">报纸<input type="radio" name="dk_message" <?php if (isset($dk_message) && $dk_message=="其他") echo "checked";?>	value="其他">其他<input type="text" name="dk_qita" value="单页" maxlength="8"/></td></tr><tr bgcolor="#ffffff" cellpadding="0" align="center" height="30">	<td >居住区域</td>	<td colspan="4" align="left"><input type="text" name="dk_home" value="" style="height:30px;width:300"/></td>	<td >工作区域</td>	<td colspan="4"><input type="text" name="dk_jop" value="" style="height:30px;width:400px"/></td></tr><tr bgcolor="#ffffff" cellpadding="0" align="center" height="30">	<td>交通工具</td>	<td colspan="4" align="left"><input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="A级车") echo "checked";?>	value="A级车" checked >A级车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="B级车") echo "checked";?>	value="B级车">B级车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="C级车") echo "checked";?>	value="C级车">C级车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="自行车") echo "checked";?>	value="自行车">自行车 <br/> <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="出租车") echo "checked";?>	value="出租车">出租车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="公交车") echo "checked";?>	value="公交车">公交车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="摩托车") echo "checked";?>	value="摩托车">摩托车 <input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="电瓶车") echo "checked";?>	value="电瓶车">电动车 </td>	<td>购买动机</td>	<td colspan="4"><input type="radio" name="dk_function" <?php if (isset($dk_function) && $dk_function=="自用") echo "checked";?>	value="自用" checked >自用 <input type="radio" name="dk_function" <?php if (isset($dk_function) && $dk_function=="投资") echo "checked";?>	value="投资">投资 <input type="radio" name="dk_function" <?php if (isset($dk_function) && $dk_function=="其他") echo "checked";?>	value="其他">其他 </td></tr><input type="submit" name="submit" value="发表"/><input type="reset" value="重填"/></form>

<input type="radio" name="dk_transport" <?php if (isset($dk_transport) && $dk_transport=="A级车") echo "checked";?>    value="A级车" checked >A级车