PHPMailer question...Sending 2 emails in one instance?

I’ve seen many examples of PHPMailer (adding a whole new email to the same object) but I just can’t understand how to apply it to my specific context… I am fairly new to PHP itself, so this is really frustrating me.
Please be so kind as to show me where exactly in my code I can send 2 emails at once… (One email goes to my own website and another goes to the person who submitted a form on my website).

Currently this code is working perfectly:

<?php
	/*...*/
	if (array_key_exists('email', $_POST)) {
    date_default_timezone_set('Etc/UTC');
    //Load Composer's autoloader
    require '../mailer/vendor/autoload.php';
    	$body = "...1";
		$body2 = "...2";
		$mail = new PHPMailer(true);                              	// Passing `true` enables exceptions
	    try {
	        //Server settings
	        //$mail->SMTPDebug = 1;                                 // Enable verbose debug output
	        $mail->isSMTP();                                      	// Set mailer to use SMTP
	        $mail->Host = 'smtp.gmail.com';                 		// Specify main and backup SMTP servers
	        $mail->SMTPAuth = true;                              	// Enable SMTP authentication
	        $mail->SMTPKeepAlive = true;							// Send messages in a single SMTP session, much faster
	        $mail->Username = 'transcriptersdesk@gmail.com';		// SMTP username
	        $mail->Password = 'secret';                           // SMTP password
	        $mail->SMTPSecure = 'tls';                            
	        $mail->Port = 587;                                    	// TCP port to connect to
	        //Recipients
	        $mail->setFrom('transcriptersdesk@gmail.com', 'Sir Francis Fish Gelatine'); //from address must be yourself! otherwise will land in spam folder as forgery
	        $mail->addAddress('info@fishgelatine.co.za', 'Sir Francis Fish Gelatine');     // Add a recipient
	        //Content
	        if ($mail->addReplyTo($_POST['email'], $_POST['fname'].' '.$_POST['lname'])) {
	        $mail->Subject = "Order #".$order_number." received on FishGelatine";
	        $mail->isHTML(true);
	        $mail->AddEmbeddedImage('../img/header.png', 'emailheader');
	        $mail->Body = $body;
	        $mail->AltBody = strip_tags($body);

	        if (!$mail->send()) {
	            //The reason for failing to send will be in $mail->ErrorInfo
	            $msg = 'Sorry, something went wrong. Please try again later.';
	        } else {
	            header("Location: ../thankyou.php?date=".$_POST['date']."&order=".$_POST['order_number']."&product=".$_POST['u_weight']."&qty=".$_POST['u_qty']."&total=".$_POST['u_total']."&fname=".$_POST['fname']."&lname=".$_POST['lname']."&delivery=".$_POST['shipping']."&addr1=".$_POST['addr1']."&addr2=".$_POST['addr2']."&addr3=".$_POST['addr3']."&addr4=".$_POST['addr4']);
	        $mail->ClearAddresses();
	        $mail->ClearAttachments();
	        //Send another email

	        /*

			//This is where I place the new email....Not working though!

	        */

	    }

	    } else {
	        $msg = 'Invalid email address, message ignored.';
	    }

	    } catch (Exception $e) {
	        echo 'Message could not be sent. Mailer Error: ', $mail->ErrorInfo;
	    }
	}
	} else {
	header("Location: ../order.php?error");
	exit();
}

But as soon as I place this piece of code inside it:

//Recipients
$mail->setFrom('transcriptersdesk@gmail.com', 'Sir Francis Fish Gelatine');
$mail->addAddress($_POST['email'], $_POST['fname'].' '.$_POST['lname']));
//Content
if ($mail->addReplyTo('info@fishgelatine.co.za', 'Sir Francis Fish Gelatine') {
$mail->Subject = "Order #".$order_number." placed on FishGelatine";
$mail->isHTML(true);
//Build a simple message body
$mail->AddEmbeddedImage('../img/header.png', 'emailheader');
$mail->Body = $body2;
$mail->AltBody = strip_tags($body2);
if (!$mail->send()) {
    //The reason for failing to send will be in $mail->ErrorInfo
    //but you shouldn't display errors to users - process the error, log it on your server.
    $msg = 'Sorry, something went wrong. Please try again later.';
} else {
	exit();
}

I get an http internal 500 error on my website. I tried placing it at different sections of the object but they won’t work. Please help!