Plugin form unable to process

Question

I'm using shortcode to process my HTML form. However, upon submit no result is being displayed. I'm not getting where I'm going wrong.

<?php
function installer(){
    include('installer.php');
}
register_activation_hook( __file__, 'installer' ); //executes installer php when installing plugin to create new database

//result display form begins

function display_result_form_fields(){
    ob_start(); ?> 
        <form id="result_form" action="" method="POST">
            <fieldset>
                <p>
                    <label for="rollNumber"><?php _e('Roll Number'); ?></label>
                    <input name="rollNumber" id="rollNumber" class="required" type="number"/>
                </p>
                <p>
                    <input type="submit" value="<?php _e('Submit'); ?>"/>
                </p>
            </fieldset>
        </form>
    <?php
    return ob_get_clean();
}

function form_processing(){
if(isset($_POST['Submit'])){
    global $wpdb;
    $student_id = $_POST['rollNumber'];
    $query = "SELECT * FROM `wp_xenonresult` WHERE `student_id` = $student_id";
    $result = $wpdb->get_row($query);
    echo "Dear student, congratulations";}
}

//shortcode begins here
function result_form() {
            form_processing();
            $output = display_result_form_fields();
            return $output;
    }

add_shortcode('result_form', 'result_form'); //create shortcode
add_filter('widget_text','do_shortcode'); // Enable shortcodes in text widgets
?>

Answer 1

You missed name attribute of <input type="submit" value="<?php _e('Submit'); ?>"/> HTML tag.

i.e.

It should be looks like: <input type="submit" name="Submit" value="<?php _e('Submit'); ?>"/>

Else, You have to change if condition inside function form_processing()

OLD: if(isset($_POST['Submit'])){

Replace with: if(isset($_POST['rollNumber'])){

Hope this will helps you.

Answer 2

With the help of @bagpipper and @AddWeb-Solution-Pvt-Ltd I finally managed to sort this issue.

<?php

function installer(){
    include('installer.php');
}
register_activation_hook( __file__, 'installer' ); //executes installer php when installing plugin to create new database

//result display form begins

function display_result_form_fields(){
    ob_start(); ?> 
        <form id="result_form" action="" method="POST">
            <fieldset>
                <p>
                    <label for="rollNumber"><?php _e('Roll Number'); ?></label>
                    <input name="rollNumber" id="rollNumber" class="required" type="number"/>
                </p>
                <p>
                    <input type="submit" name = "submit" value="Submit"/>
                </p>
            </fieldset>
        </form>
    <?php
    return ob_get_clean();
}

function form_processing(){
    global $wpdb;
    $student_id = $_POST['rollNumber'];
    $query = "SELECT * FROM `wp_xenonresult` WHERE `student_id` = $student_id";
    $result = $wpdb->get_row($query);
    echo "Dear ".$result->", ";
    }


//shortcode begins here
function result_form() {
    ob_start(); 
    if(isset($_POST['submit'])){
        form_processing();
        }
    else{
        $output = display_result_form_fields();
        return $output;
    }
    return ob_get_clean();
    }

add_shortcode('result_form', 'result_form'); //create shortcode
add_filter('widget_text','do_shortcode'); // Enable shortcodes in text widgets
?>