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    Home Backend Development PHP Tutorial How can I dynamically populate a second drop-down box based on the selection in a first drop-down box using jQuery and PHP?

    How can I dynamically populate a second drop-down box based on the selection in a first drop-down box using jQuery and PHP?

    Dec 23, 2024 am 08:18 AM

    How can I dynamically populate a second drop-down box based on the selection in a first drop-down box using jQuery and PHP?

    Dynamically Populating Drop-Down Boxes

    A popular technique used in web development is to create interactive web forms where drop-down boxes can display options that depend on the selected value of a preceding drop-down box. This functionality is commonly achieved using a combination of JavaScript (jQuery) and server-side scripting (PHP).

    Example Code Explanation

    In this specific scenario, you are trying to populate the second drop-down box based on the value selected in the first drop-down box. The code provided accomplishes this by using the following steps:

    1. Capturing the User's Selection: When the user changes the selection in the first drop-down box, a jQuery event handler is triggered. This handler captures the value of the selected option using $(this).val().
    2. Sending a Request: Using jQuery's AJAX capabilities, an asynchronous request is sent to the server-side PHP script, another_php_file.php. Along with the request, the value of the selected option sel_stud is passed as data.
    3. Server-Side Processing: The another_php_file.php script receives the posted data, performs the necessary database queries to retrieve relevant data specific to the selected option, and assembles a response containing HTML markup for the updated second drop-down box.
    4. Updating the Drop-Down Box: The response received from the server is processed by the AJAX success handler function. The HTML markup for the second drop-down box is injected into the DOM using $('#LaDIV').html(whatigot);.

    Customized Example

    This code example demonstrates a customized implementation where the first drop-down box is used to select student names. Upon selection, the second drop-down box displays the corresponding classes taught by that student.

    tester.php

    <html>
    <head>
        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
        <script type="text/javascript">
            $(function() {
                $('#stSelect').change(function() {
                    var sel_stud = $(this).val();
                    $.ajax({
                        type: "POST",
                        url: "another_php_file.php",
                        data: 'theOption=' + sel_stud,
                        success: function(whatigot) {
                            $('#LaDIV').html(whatigot);
                        }
                    });
                });
            });
        </script>
    </head>
    <body>
    
        <select name="students">

    another_php_file.php

    <?php
    
        // Database Connection
        $server = 'localhost';
        $login = 'root';
        $pword = '';
        $dbname = 'test';
        mysql_connect($server,$login,$pword) or die($connect_error);
        mysql_select_db($dbname) or die($connect_error);
    
        // Get POST Data
        $selStudent = $_POST['theOption'];
    
        // Query Database
        $query = "SELECT * FROM `class` WHERE `teacher_id` = $selStudent";
        $result = mysql_query($query) or die('Fn Error: ' . mysql_error());
        $num_rows_returned = mysql_num_rows($result);
    
        // Build Response HTML
        $r = '
            <select>
        ';
    
        if ($num_rows_returned > 0) {
            while ($row = mysql_fetch_assoc($result)) {
                $r = $r . '<option value="' . $row['id'] . '">' . $row['name'] . '</option>';
            }
        } else {
            $r = '<p>No classes taught by this student</p>';
        }
    
        // Echo Response
        echo $r;
    ?>

    This customized solution tailors the second drop-down box to display classes based on the selected student, providing a flexible and user-friendly form experience for dynamically populated drop-down boxes.

    The above is the detailed content of How can I dynamically populate a second drop-down box based on the selection in a first drop-down box using jQuery and PHP?. For more information, please follow other related articles on the PHP Chinese website!

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