How To Fix WordPress custom plugin problems which shows - "Database Update Required"

Question

How To Fix WordPress custom plugin problems which shows - "Database Update Required" - Even though the plugin works fine. I have attached an image of the error/warning message. The code-snipet includes all the source-code from the plugin. I don't know how to remove the error/warning message.

<?php
/**
* Plugin Name: Content Creator 2 plugin
* Plugin URI: http://www.nodomain.com
* Description: This plugin will create a simple HTML-form with 3 input fields and store the information into a stage table.
* Version: 1.0
* Author: Murat Kilic
* Author URI: http://www.nodomain.com
* License: GPLv3
**/

function insert_into_db() {
    # This ($wpdb) is a global variable inside WordPress that gives me access to create new tables inside WordPress
    global $wpdb;
    
    #Create a new table inside my existing wp-database if table not exists
    $table = $wpdb->prefix . "cc2testplugin";
    #Setting the charset for the database
    $charset_collate = $wpdb->get_charset_collate();
    # Creating table with SQL
    $sql = "CREATE TABLE IF NOT EXISTS $table (
    `id` MEDIUMINT NOT NULL AUTO_INCREMENT,
    `stagename` TEXT NOT NULL,
    `capacity` MEDIUMINT NOT NULL,
    `url` TEXT NOT NULL,
    UNIQUE (`id`)
    ) $charset_collate;";
    
    #Including upgrade.php file
    require_once( ABSPATH . 'wp-admin/upgrade.php');
    
    #Useful for creating new tables and updating existing tables to a new structure.
    dbDelta ($sql);
    
    #Starts output buffering
    ob_start();
    
    ?>
      
    <!-- Here I will create my HTML_form with 3 input-fields  -->
    <form action="#v_form" method="post" id="v_form">
        <label for="stagename">
            <h3>Name of stage:</h3>
        </label>
        <input type="text" name="stagename" id="stagename">
        
        <label for="capacity">
            <h3>Max capacity of stage:</h3>
        </label>
        <input type="number" min="1000" max="50000" name="capacity" id="capacity">
        
        <label for="url">
            <h3>Type MAP location (url):</h3>
        </label>
        <input type="url" name="url" id="url">
        <input type="submit" value="submit" name="submit_form">
    </form>
    <!-- END HTML-form -->
      
    <?php
        #Gets the current buffer contents and delete current output buffer
        $html = ob_get_clean();
        # Check if the user has clicked on the submit button
        if (isset ($_POST["submit_form"])  ) {
            #Setting table prefix
            $table = $wpdb->prefix . "cc2testplugin";
            #Collecting data from input fields and store it in variables
            $stagename = strip_tags($_POST["stagename"], "");
            $capacity = strip_tags($_POST["capacity"], "");
            $url = $_POST["url"];
            
            #Inserting data from the HTML-form based on the variables into the table
            $wpdb->insert(
                $table,
                array(
                    'stagename' => $stagename,
                    'capacity' => $capacity,
                    'url' => $url
                )
            );
            #Writing out a message after having inserted the data from the HTML-Form
            $html = "<p>The stage with following name <strong>$stagename</strong> was successfully inserted! Thanks.</p>";
        }
    # Displays /outputs text on screen
    return $html;
}
    #Adding a wordpress shortcode that can be used on either a wordpress page or post
    add_shortcode('cc2testplugin','insert_into_db');    
    ?>

Answer 1

The problem I see here is that you are checking to create the table EVERY SINGLE TIME a page with the shortcode on it is run. When you create the table, you include the upgrade.php which will show the message you describe.

What you need to do is break off the piece that creates the table (including the call to upgrade.php) and add that to your activate plugin piece instead. You should only need to check and create that table once. Don't forget to remove the table (and anything else you add in) on plugin uninstall.

Read up more about it here: https://codex.wordpress.org/Creating_Tables_with_Plugins