After form submission want to show success message in the form page

Question

Admin side I submit form to admin-post.php. I want to print success message in the bottom of the form. Iam new in wordpress what i did shown below.

admin.php?page=add-products form code

 <form action="<?php echo admin_url('admin-post.php') ?>" method="post">
                <table>
                <input type="hidden" name="action" value="add_product_from_admin">
                <tr><td>Name</td><td><input type="text" name="pr_name" id="pr_name"></td></tr> 
    <tr><td colspan="2" align="center"><input type="submit" name="pr_submit" id="pr_submit" value="Save Products"></td></tr>
                </table>
            </form>


    add_action( 'admin_post_add_product_from_admin', 'add_product_into_data_base' );



function add_product_into_data_base() {
    //some database operations
wp_redirect(admin_url('admin.php?page=add-products&message=success'));
}

Answer 1

You need to pass the variable and its value in GET method to display the success message which you're already doing.

Now, in your PHP file, display a message based on the GET parameter and its value.

if($_GET['message'] == 'success'){ 
  //display your message 
}