这个准备好的语句可以防止SQL注入吗？

$string = trim($_POST['string'])
$sql = "INSERT INTO table (string) VALUES(:string)";
$query = $db->prepare($sql);
$query->execute(array(
    ":string" => $string
));

此代码块可以防止SQL注入吗？

编辑：
这是我正在与数据库的连接。此代码的字符集是否允许执行以上代码块并防止SQL注入？

//database credentials
define('DBHOST','localhost');
define('DBUSER','root');
define('DBPASS','');
define('DBNAME','table');

//application address
define('DIR','http://localhost/');
define('SITEEMAIL','[email protected]');

try {

//create PDO connection 
$db = new PDO("mysql:host=".DBHOST.";port=3306;dbname=".DBNAME, DBUSER, DBPASS);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

} catch(PDOException $e) {
//show error
echo 'Looks like server is down please check back later';
exit;
}