How to hide the form after successful php execution

Question

I want to hide the form after someone has entered the input in my plugin form and has hit submit button. However, as I'm using shortcode function in my plugin file I am unable to use simple html to display form and hide it traditionally.

How do I hide this form? This is my php script of the plugin file:

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

add_action('admin_menu','result_menu'); //wordpress admin menu creation
function result_menu()
{
    add_menu_page('Result','Result','administrator','xenon-result');
    add_submenu_page( 'xenon-result', 'Manage Marks', ' Manage Marks', 'administrator', 'Manage-Xenon-Marks', 'Xenon_Marks' );
}
function Xenon_Marks() //function to add marks addition form in admin view
{
    include('new/result-add-marks.php');
}

function html_form_code() 
{
echo '<h3 align="center" class="titlehead"><br><b>Shikhar Entrance Test - 2017 Result</b></h3>';
echo '<form action="" method="post" name="display_form">';
echo '<fieldset>';
echo '<legend>Student Information</legend>';
echo 'Roll Number: <input type="number" min="170001" max="171000" name="rollNumber"><br>';
echo '<input type="submit">';
echo '<input type ="reset">';
echo '</form>';
}

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

if(isset($_POST['submit']))
{
   result_display();
}

//shortcode for the plugin begins.
function display_shortcode() {
    ob_start();
    result_display();
    html_form_code();
    return ob_get_clean();
}

add_shortcode( 'xenon_result_display', 'display_shortcode' );
// Enable shortcodes in text widgets
add_filter('widget_text','do_shortcode');
?>

Answer 1

If I understand the code correctly, you are wanting to make the result_display() function call conditional by moving the post check to inside the shortcode function. ie.

function display_shortcode() {
    ob_start();
    if (isset($_POST['submit'])) {result_display();}
    else {html_form_code();}
    return ob_get_clean();
}