PHP - Php Sendmail Stopped Working??? Help

The code below worked perfectly on my old hosting service.   I've had to move to a new host and I get this error when I try to run the code.

Warning: Cannot modify header information - headers already sent by (output started at ../user/dbconfig.php:11)

This is the code:-

<?php
// connect to DATABASE!
include_once('../user/dbconfig.php');

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

$options = [
    \PDO::ATTR_ERRMODE            => \PDO::ERRMODE_EXCEPTION,
    \PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC,
    \PDO::ATTR_EMULATE_PREPARES   => false,
];

$dsn = "mysql:host=$host;dbname=$dbname;charset=$charset;port=$port";
try {
    // create a PDO connection with the configuration data
    $conn = new PDO($dsn, $user, $dbpassword, $options);
    
} catch (PDOException $e) {
    // report error message
    echo $e->getMessage();
}

    $ans = $_POST['answer'];
//Setup the filename that our CSV will have when it is downloaded.
if($ans == 'yes'){
    $fileName = 'answers-right.csv';
} elseif ($ans == 'no') {
    $fileName = 'answers-wrong.csv';
}

    // Create our SQL query.
    $sql = 'SELECT ID,email,firstname,lastname,message FROM checks WHERE answer = ?';
    $stmt = $conn->prepare($sql);
    $stmt->execute([$ans]);
    $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);      // NB: now using fetchAll because there's going to be more than one record

    //Get the column names.
$columnNames = array();
if(!empty($rows)){
    //We only need to loop through the first row of our result
    //in order to collate the column names.
    $firstRow = $rows[0];
    foreach($firstRow as $colName => $val){
        $columnNames[] = $colName;
    }
}
 
//If the file exists and is writeable then delete it
if(is_writable($fileName)){
    //Delete the file
    $deleted = unlink($fileName);
}

//Set the Content-Type and Content-Disposition headers to force the download.
header('Content-Type: application/excel');
header('Content-Type: application/excel Content-Disposition: attachment; filename="' . $fileName . '"');

//Open up a file pointer
$fp = fopen('php://output', 'w');
 
//Start off by writing the column names to the file.
fputcsv($fp, $columnNames);
 
//Then, loop through the rows and write them to the CSV file.
foreach ($rows as $row) {
    fputcsv($fp, $row);
}
 
//Close the file pointer.
fclose($fp);
?>

Would appreciate some help please?

<?

// edit these lines

$your_name="Company Name";

$your_email="sarah@companyname.co.uk";

$your_web_site_name="companyname.co.uk";





?>



               <?php

               //If the form is submitted

               if(isset($_POST['name'])) {

                  

                     //Check to make sure that the name field is not empty

                     if(trim($_POST['name']) === '') {

                        $nameError = 'Please enter your name.';

                        $hasError = true;

                     } else {

                        $name = trim($_POST['name']);

                     }

                     

                     //Check to make sure sure that a valid email address is submitted

                     if(trim($_POST['email']) === '')  {

                        $emailError = 'Please enter your email address.';

                        $hasError = true;

                     } else if (!eregi("^[A-Z0-9._%-]+@[A-Z0-9._%-]+\.[A-Z]{2,4}$", trim($_POST['email']))) {

                        $emailError = 'You entered an invalid email address.';

                        $hasError = true;

                     } else {

                        $email = trim($_POST['email']);

                     }

                        

                     //Check to make sure comments were entered   

                     if(trim($_POST['message']) === '') {

                        $commentError = 'Please enter your message.';

                        $hasError = true;

                     } else {

                        if(function_exists('stripslashes')) {

                           $comments = stripslashes(trim($_POST['message']));

                        } else {

                           $comments = trim($_POST['message']);

                        }

                     }

                        

                     //If there is no error, send the email

                     if(!isset($hasError)) {



                        $emailTo = $your_email;

                        $subject = 'Contact Form Submission from '.$name;

                        $body = "Name: $name \n\nEmail: $email \n\nPhone: ".trim($_POST['phone'])." \n\nComments: $comments";

                        $headers = 'From: '.$your_web_site_name.' <'.$emailTo.'>' . "\r\n" . 'Reply-To: ' . $email;

                        

                        mail($emailTo, $subject, $body, $headers);



                        $emailSent = true;



                  }

               }

               

               ?>







<?php if(isset($emailSent) == true) { ?>

   <div class="ok">

      <h1>Thanks, <?php echo $name;?></h1>

      <p>Your email was successfully sent. We will be in touch soon.</p>

   </div>

<?php } ?>





<?php if(isset($hasError) ) { ?>

   <div class="error2">There was an error submitting the form.</div>

<?php } ?>

We had to update our Linux server from php 5.4 to php 7.4.  Something has changed and I have a feeling it is due to changes in fputcsv.

When running the code below, instead of opening a csv file in libre calc, it fills the browser with the result.  Is there a way of fixing this so I get the csv file again?

<code>date_default_timezone_set("America/New_York");
$filename = "import.csv";
$fp = fopen('php://output', 'w');
header('Content-type: application/csv');
header('Content-Disposition: attachment; filename='.$filename);
$then = time() - 3601;
$query = "SELECT * FROM ppb_listings where user_id = '4' and unix_timestamp(start_time) > $then";
$result = mysqli_query($conn, $query);
while($row = mysqli_fetch_row($result)) {
    fputcsv($fp, $row);
}
echo $result;
exit;
?>

</code>

Thanks for any help.