How to send an email using wp_mail and using more than one BCC in the header

Question

I have this code part that's responsible for getting the variables from the contact form - and and sending an email to me, and my friends from work.

add_action('wp_ajax_nopriv_submit_contact_form', 'submit_contact_form'); 
// Send information from the contact form
function submit_contact_form(){

    // If there is a $_POST['email']...
    if( isset($_POST['email']) && ($_POST['validation'] == true ) ) {

        $email = $_POST['email'];       
        $email_to = "[email protected]";
        $fullname = $_POST['fullname'];
        $headers = 'From: '. $fullname .' <'. $email .'>' . "\r\n";
        $group_emails = array(
            '[email protected]', 
            '[email protected]', 
            '[email protected]', 
            '[email protected]', 
            '[email protected]' 
            );
        $email_subject = "example intro: $email";
        $message = $_POST['text']; 

        if(wp_mail($group_emails,$email_subject,$message,$headers)) {
            echo json_encode(array("result"=>"complete"));
        } else {
            echo json_encode(array("result"=>"mail_error"));
            var_dump($GLOBALS['phpmailer']->ErrorInfo);
    }
        wp_die();
    }
}

I want to add to the headers 4 emails as BCC.

How do I do this right? I tried a few variations of writing it without any success.

Answer 1

$headers can be a string or an array, but it may be easiest to use in the array form. To use it, push a string onto the array, starting with "From:", "Bcc:" or "Cc:" (note the use of the ":"), followed by a valid email address.

https://codex.wordpress.org/Function_Reference/wp_mail#Using_.24headers_To_Set_.22From:.22.2C_.22Cc:.22_and_.22Bcc:.22_Parameters

In other words:

$headers = array(
    'From: [email protected]', 
    'CC: [email protected]', 
    'CC: [email protected]', 
    'BCC: [email protected]', 
    'BCC: [email protected]' 
);

You can see where the Core parses the string by splitting it on that ":":

296  list( $name, $content ) = explode( ':', trim( $header ), 2 );
297 
298                                 // Cleanup crew
299                                 $name    = trim( $name    );
300                                 $content = trim( $content );
301 
302                                 switch ( strtolower( $name ) ) {
303                                         // Mainly for legacy -- process a From: header if it's there
304                                         case 'from':

Note: This is untested but I am fairly confident. I did not want to start sending email to addresses without warning (if those are even active addresses).