Column count doesn't match value count at row 1

PHP存储注册表单提示Column count doesn't match value count at row 1 错误请问是什么原因？
下面是执行代码$mysql_username="site_database";
$mysql_userpass="site_database";
$mysql_server="localhost";
$mysql_database="site_database_2007";$conn=mysql_connect($mysql_server,$mysql_username,$mysql_userpass) or die("不能连接数据库服务器！");
mysql_select_db($mysql_database,$conn);
mysql_query ('set names "gbk"');$sql="insert into site_member values (null,'$member_mail','$member_password','$member_name','$member_nickname','$member_sex','$member_idnuber','$member_city','$member_contact','$member_status','$member_pic','$member_regip','$member_regtime')";mysql_query($sql)or die(mysql_error());