How can I use a PHP function to include a file based on a GET parameter and load a default file if the GET parameter is not set?

I want to ensure that the correct file is loaded depending on whether the GET parameter site is present or not. Can someone tell me what I am doing wrong or how to get this right?
I need also an MakeStatement function. The parameters are: $query and $array is there anything to improve about this code? Thanks!

Can anyone help me to complete my code or write it correctly?

function getSite($site) {
    if(isset($_GET['site'])) {
        include_once($_GET['site']);
    } else {
        include_once($site);
    }
}

function makeStatment($query, $array = null)
{
    $stmt = $con->prepare($query);
    $stmt->execute($array);
    return $stmt;
}

>Solution :

try using this

function getSite($site)
{
    if(isset($_GET['site']))
    {
        include_once('site/'.$_GET['site'].'.php');
    } 
    else
    {
        include_once('site/'.$site.'.php');
    }
}

function makeStatment($query, $array = null)
{
    try 
    {
        global $con;
        $stmt = $con->prepare($query);
        $stmt->execute($array);
        return $stmt;
    } 
    catch (Exception $e)
    {
        return $e;
    }
}