Province and city menu linkage, AJAX level 3 menu linkage_PHP tutorial

First look at the extension of JQ as follows:

//city selected

jQuery.fn.cityselect = function(n,s1,s2,s3) {
if ((n!=3)&&(n!=2)) {n=2};
if (s1=="") {s1="province"};
if (s2=="") {s2="city"};
if (s3=="") {s3="area"};

if (n==2){//Second level linkage
//alert(s1+$("select[@name="+s1+"] option[@selected]").val());
​​​ $("select[@name="+s1+"]").bind("change",function(event) {
$.ajax({
        type: "GET",
URL: "/inc/lib/ajax_city.php",
data: "n=v2&cityid="+$("select[@name="+s1+"] option[@selected]").val(),
Success: function(opt){$("select[@name="+s2+"]").empty().append(opt);}
        });
});

}

if (n==3){//Three-level linkage

$("select[@name="+s1+"]").bind("change",function(event) {
$.ajax({
        type: "GET",
URL: "/inc/lib/ajax_city.php",
data: "n=v2&cityid="+$("select[@name="+s1+"] option[@selected]").val(),
Success: function(opt){
           $("select[@name="+s2+"]").empty().append(opt);
               $.ajax({
          type: "GET",
​​​​​ url: "/inc/lib/ajax_city.php",
              data: "n=v3&cityid="+$("select[@name="+s2+"] option[@selected]").val(),
Success: function(opt){
               $("select[@name="+s3+"]").empty().append(opt);
            }
          });
          }
        });
});
$("select[@name="+s2+"]").bind("change",function(event) {
$.ajax({
Type: "GET",
URL: "/inc/lib/ajax_city.php",
data: "n=v3&cityid="+$("select[@name="+s2+"] option[@selected]").val(),
Success: function(opt){ $("select[@name="+s3+"]").empty().append(opt);}
});

});

}

};

The next function in PHP is as follows ========

//City linkage script
function cityselect($n=2,$s1=province,$s2=city,$s3=area,$v1=320000,$v2=320500,$v3=320501){
$db = new DB_Sql; //Initialize database
$db->connect(DB_Database, DB_Host, DB_User, DB_Password); //Database connection
$db->DB_Sql("set names gbk");
//Linked AJAX script
$tmp = " ";
//Province selection
$tmp .= " ";
$db->query("select * from sz_chinacity where right(CityPostCode, 4) = 0000 order by CityID asc");
while ($db->next_record()){
If ($db->Record[CityPostCode]==$v1){
$tmp .= "Record[CityPostCode]."" selected>".$db->Record[CityName]." ";
}else{
$tmp .= "Record[CityPostCode]."">".$db->Record[CityName]." ";
}
}
$tmp .= " ";
//City selection
$tmp .= " ";
$cityid = substr($v1,0,2);
$db->query("select * from sz_chinacity where Right(CityPostCode, 2) = 00 and Left(CityPostCode, 2)=".$cityid." and Right(CityPostCode, 4) <> 0000 order by CityID asc");
while ($db->next_record()){
If ($db->Record[CityPostCode]==$v2){
$tmp .= "Record[CityPostCode]."" selected>".$db->Record[CityName]." ";
}else{
$tmp .= "Record[CityPostCode]."">".$db->Record[CityName]." ";
}
}
$tmp .= " ";


if ($n==3){
//Region selection
$tmp .= " ";
$cityid = substr($v2,0,4);
$db->query("select * from sz_chinacity where Left(CityPostCode, 4)=".$cityid." and Right(CityPostCode, 2) <> 00 order by CityID asc");
while ($db->next_record()){
If ($db->Record[CityPostCode]==$v3){
$tmp .= "Record[CityPostCode]."" selected>".$db->Record[CityName]." ";
}else{
$tmp .= "Record[CityPostCode]."">".$db->Record[CityName]." ";
}
}
$tmp .= " ";
}
echo $tmp;
}

When calling: