Array in DB word niet juist ge-update (Opgelost)

<?php
$database_string = "10-20-30-40";

if(isset($_POST['go']))
{
	if(isset($_POST['optie']))
	{
		$array_values = explode("-", $database_string);
		switch ($_POST['optie'])
		{
			case 1:
				$erbij = 1;
				$array_values[0] += $erbij;
			break;
			case 2:
				$erbij = 2;
				$array_values[1] += $erbij;
			break;
			case 3:
				$erbij = 3;
				$array_values[2] += $erbij;
			break;
			case 4:
				$erbij = 4;
				$array_values[3] += $erbij;
			break;
		}
		echo implode("-", $array_values);
	}
	else
	{
		echo 'kies iets..';
	}
}
?>

<form action="" method="post">
    1<input name="optie" type="radio" value="1" />
    2<input name="optie" type="radio" value="2" />
    3<input name="optie" type="radio" value="3" />
    4<input name="optie" type="radio" value="4" />
    <input name="go" type="submit" />
</form>

<?php
$database_string = "10-20-30-40";
 
if(isset($_POST['go']))
{
	if(isset($_POST['optie']))
	{
		$array_values = explode("-", $database_string);
		switch ($_POST['optie'])
		{
			case 1:
				$erbij = 1;
				$array_values[0] += $erbij;
			break;
			case 2:
				$erbij = 2;
				$array_values[1] += $erbij;
			break;
			case 3:
				$erbij = 3;
				$array_values[2] += $erbij;
			break;
			case 4:
				$erbij = 4;
				$array_values[3] += $erbij;
			break;
		}
		echo implode("-", $array_values);
	}
	else
	{
		echo 'kies iets..';
	}
}
?>
 
<form action="" method="post">
    1<input name="optie" type="radio" value="1" />
    2<input name="optie" type="radio" value="2" />
    3<input name="optie" type="radio" value="3" />
    4<input name="optie" type="radio" value="4" />
    <input name="go" type="submit" />
</form>