<?php
$con=mysqli_connect("localhost","root","","vb");
// Check connection
if (mysqli_connect_errno())
{
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

// escape variables for security
$firstname = mysqli_real_escape_string($_POST['Forename']);
$lastname = mysqli_real_escape_string($_POST['Surname']);
$email = mysqli_real_escape_string($_POST['Email']);

$sql="INSERT INTO 'customer1' ('Forename', 'Surname', 'Email')
VALUES ($Forename, $Surname, $Email)";

if (!mysqli_query($con,$sql))
{
  die('Error: ' . mysqli_error($con));
}
echo "1 record added";

mysqli_close($con);
?>

$sql="INSERT INTO customer1 (Forename, Surname, Email)
VALUES ('$Forename', '$Surname', '$Email')";

$sql="INSERT INTO `customer1` (`Forename`, `Surname', `Email`)
VALUES ($Forename, $Surname, $Email)";

$sql='INSERT INTO  customer1  (`Forename`, `Surname`, `Email`)
VALUES ("'.$Forename.'","'.$Surname.'", "'.$Email.'")';