ajax实现无限级联动含数据库版，想读取一个下拉框的值(动态的),作为后台调用出另一个表中的值,不同的调出来的值都不同,-ajax unlimited level interaction　containing version and want to read the value of a drop-down box (dynamic), as a background calling out another table values, different values ​ ​ are different tune out,