Dougless on "PHP - how do i stop my loop to register data twice?"

Hi community.

I am facing a problem here.

The code below is running on my site and when i fill in the form and check my database the data has been registered twice.

Please the the following php code from my functions.php file.

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>';
	  	} //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
  	};

  	add_shortcode('map_location_report','map_location_report_form');

How do i stop this code from registering the data twice?

Thanks in advance