<?php
$connection=mysqli_connect("host", "username", "password", "database");
$sql="SELECT COUNT(*) from database_users";
$stmt = $connection->prepare($sql);
$stmt->execute();
$res = $stmt->get_result();
$users = $res->fetch_array(MYSQLI_ASSOC);
if ($users['COUNT(*)'] < 4) {
?>
// html goes here, outside of the php tags
<?php
} else {
echo "Sorry, you have reached the user account limit.";
};
?>