Dougless on "WordPress - how to solve double submission in form on page?"

I got an ongoing issue with a form on a page in WordPress. I have defined my form in the functions.php file and then calling the form on a page, but it is submitting data twice. How can i solve this?

The code looks as following:

This is the do_action function i use on the actual page

<?php do_action('map_location_form'); ?>

...and this is the form defined in my function.php file:

add_action('map_location_form', 'map_location_report_form');

function map_location_report_form()
{
    global $wpdb;

    $this_page  =   $_SERVER['REQUEST_URI'];
    $page       =   $_POST['page'];

    if ( $page == NULL )
    {
        echo '<form method="post" action="' . $this_page .'">

                <div class="formfield-report" id="formfield-report-firstname">
                    <label for="first_name" id="first_name">Navn: </label>
                    <input type="text" name="first_name" id="first_name" />
                </div>

                <div class="formfield-report" id="formfield-report-lastname">
                    <label for="last_name" id="last_name">Efternavn: </label>
                    <input type="text" name="last_name" id="last_name" />
                </div>

                <div class="formfield-report" id="formfield-report-locationtype">
                    <label for="location_type" id="location_type">Rapport type: </label>
                    <select name="location_type" />
                        <option value="sigtmelding" selected>Sigtmelding</option>
                        <option value="fangstrapport">Fangstrapport</option>
                        <option value="jagtomraade">Jagtområde</option>
                    </select>
                </div>

                <div class="formfield-report" id="formfield-report-latitude">
                    <label for="location_latitude" id="location_latitude">Breddegrad: </label>
                    <input type="text" name="location_latitude" id="location_latitude" />
                </div>

                <div class="formfield-report" id="formfield-report-longitude">
                    <label for="location_longitude" id="location_longitude">Længdegrad: </label>
                    <input type="text" name="location_longitude" id="location_longitude" />
                </div>

                <input type="hidden" value="0" name="page" />

                <div id="formfield-report-button">
                    <input class="btn btn-default submit-form-button" type="Submit" />
                </div>

        </form>';
        wp_redirect(WP_HOME.'/news.php');
    } //End Page 1 of Form
    // Start Page 2 of Form
    elseif ( $page == 0 )
    {
        $first_name             =   $_POST['first_name'];
        $last_name              =   $_POST['last_name'];
        $location_type          =   $_POST['location_type'];
        $location_latitude      =   $_POST['location_latitude'];
        $location_longitude     =   $_POST['location_longitude'];
        $page                   =   $_POST['page'];

        $page_one_table = 'maplocationreports';

        $page_one_inputs =  array
        (
            'first_name'            => $first_name,
            'last_name'             => $last_name,
            'location_type'         => $location_type,
            'location_latitude'     => $location_latitude,
            'location_longitude'    => $location_longitude,
            'page'                  => $page
        );

        $insert_page_one = $wpdb->insert($page_one_table, $page_one_inputs);

        echo '<h3>Mange tak for dit bidrag!</h3>';
        echo '<p>Der er sat stor pris på at du har taget dig tid til at registrere et punkt på kortet!</p>';

    } // End Page 2 of Form
};

How can i solve the issue so that the form only sumbits one row of data to my database?

I have seen another solution where i do not get a double submission to my database but then the form is showed in my header area which it should not. The code for that is as following:

add_action('map_location_form', 'map_location_report_form');

function map_location_report_form()
{
    global $wpdb;

    $this_page  =   $_SERVER['REQUEST_URI'];
    $page       =   $_POST['page'];

    if ( $page == NULL )
    {
        echo '<form method="post" action="' . $this_page .'">

                <div class="formfield-report" id="formfield-report-firstname">
                    <label for="first_name" id="first_name">Navn: </label>
                    <input type="text" name="first_name" id="first_name" />
                </div>

                <div class="formfield-report" id="formfield-report-lastname">
                    <label for="last_name" id="last_name">Efternavn: </label>
                    <input type="text" name="last_name" id="last_name" />
                </div>

                <div class="formfield-report" id="formfield-report-locationtype">
                    <label for="location_type" id="location_type">Rapport type: </label>
                    <select name="location_type" />
                        <option value="sigtmelding" selected>Sigtmelding</option>
                        <option value="fangstrapport">Fangstrapport</option>
                        <option value="jagtomraade">Jagtområde</option>
                    </select>
                </div>

                <div class="formfield-report" id="formfield-report-latitude">
                    <label for="location_latitude" id="location_latitude">Breddegrad: </label>
                    <input type="text" name="location_latitude" id="location_latitude" />
                </div>

                <div class="formfield-report" id="formfield-report-longitude">
                    <label for="location_longitude" id="location_longitude">Længdegrad: </label>
                    <input type="text" name="location_longitude" id="location_longitude" />
                </div>

                <input type="hidden" value="0" name="page" />

                <div id="formfield-report-button">
                    <input class="btn btn-default submit-form-button" type="Submit" />
                </div>

        </form>';
        wp_redirect(WP_HOME.'/news.php');
    } //End Page 1 of Form
    // Start Page 2 of Form
    elseif ( $page == 0 )
    {
        $first_name             =   $_POST['first_name'];
        $last_name              =   $_POST['last_name'];
        $location_type          =   $_POST['location_type'];
        $location_latitude      =   $_POST['location_latitude'];
        $location_longitude     =   $_POST['location_longitude'];
        $page                   =   $_POST['page'];

        $page_one_table = 'maplocationreports';

        $page_one_inputs =  array
        (
            'first_name'            => $first_name,
            'last_name'             => $last_name,
            'location_type'         => $location_type,
            'location_latitude'     => $location_latitude,
            'location_longitude'    => $location_longitude,
            'page'                  => $page
        );

        $insert_page_one = $wpdb->insert($page_one_table, $page_one_inputs);

        echo '<h3>Mange tak for dit bidrag!</h3>';
        echo '<p>Der er sat stor pris på at du har taget dig tid til at registrere et punkt på kortet!</p>';

    } // End Page 2 of Form
};

Do anybody know how I can work around this?

Please be specific and elaborate :)