Inserting form data into database using PDO using if statement

try {
$results = $db->prepare("INSERT INTO Form_Data
                        (first_name, last_name, email, gender, comment)
                        VALUES
                        (?,?,?,?,?) 
                        ");
$results->bindParam(1,$fname,PDO::PARAM_STR);
$results->bindParam(2,$lname,PDO::PARAM_STR);
$results->bindParam(3,$email);
$results->bindParam(4,$gender);
$results->bindParam(5,$comment,PDO::PARAM_STR);

if ($_SERVER["REQUEST_METHOD"] == "POST") { 
    $results->execute();
}

} catch (Exceptions $e) {
echo "Unable to insert data";
exit;
}

Do I need to use the if($_SERVER["REQUEST_METHOD] == "POST") statement? Or can I just use $results->execute();? And why?