jQuery combined with PHP MySQL to implement secondary linkage drop-down list [Example]_jquery

Implementation principle: According to the change of province value, sf_id is passed to the background php file for processing through jQuery. PHP queries the MySQl database to get the corresponding city name, and returns JSON data to the front-end for processing, that is, the linkage effect is achieved!

For the convenience of explanation, the provinces are given directly here: Henan Province (sf_id=1) Zhejiang Province (sf_id=2), and two data tables are created for city and student information respectively! The encoding methods are all: utf8! Create a new database and execute the following SQL statements!

Copy code The code is as follows:

/* City table*/
create TABLE IF NOT EXISTS `dishi`(
`ds_id` int(3) auto_increment not null primary key,
`sf_id` int(3) not null default '0',
`ds_name` varchar(50) not null
);
/* student table*/
create TABLE IF NOT EXISTS `xuesheng`(
`xs_id` int(3) auto_increment not null primary key,
`ds_id` int(3) not null default '0',
`xs_name` varchar(50) not null
); Then set up a front desk shelf:

Copy code The code is as follows:

Province	Henan Province Zhejiang Province < ;/td>
Prefecture and city
Student name

Then comes the jQuery part. For details, please see the comments after the code:

Copy code The code is as follows:

The select.php is the key part. This file receives the parameter sf_id passed by the front desk through the $.getJSON method, and then select.php obtains the corresponding city data based on the province sf_id, and then returns the JSON data. The front desk uses jQuery to convert the JSON The data is processed and written into , and the linkage effect is completed!

Copy code The code is as follows:

$sf_id = $_GET["sf_id"];
if(isset($sf_id)){
$q=mysql_query("select * from dishi where sf_id = $sf_id");
while($row=mysql_fetch_array($q)){
$select[] = array("ds_id"=>$row['ds_id'],"ds_name"=>urlencode($row['ds_name']));
}
echo urldecode(json_encode ($select));
}

The urlencode() and urldecode() functions are to prevent the Chinese database content from being garbled! It should also be noted here that select.php must not return any other data to avoid JSON returning an error!

Finally, some children asked that this effect can be used conveniently when adding student information. If there is passed student information that needs to be edited, the city where the student to be edited cannot be directly displayed! Here you need to make a judgment:

First make a judgment on the above:

Copy code The code is as follows:

$sql="SELECT * FROM dishi WHERE ds_id=".$ds_id;
$resultds=mysql_query($sql,$conn);
while($listds=mysql_fetch_array($resultds)){ ?>

Then when the page is loaded, make a judgment before executing the getVal() function for the first time. Please see the comments section for instructions:

Copy code The code is as follows:

$().ready(function(){
//When $ds_id is not empty, it means loading When modifying the status of the form, the getVal() function cannot be called immediately when the page is loaded to avoid being unable to display the income and expenditure category of the account to be modified
//When $ds_id is empty, it means loading the add form. At this time, the getVal() function must be called immediately when the page is loaded to display the subcategory of the current income and expenditure type
getVal();
< ?php } ?>
$("#sf_id").change(function(){
getVal();
});
});

Okay, it's almost over!