In what situations should PHP developers consider using CC or BCC when sending emails to multiple recipients?

When sending emails to multiple recipients, PHP developers should consider using CC (Carbon Copy) or BCC (Blind Carbon Copy) when they want to include additional recipients without the other recipients knowing. CC is used when the recipients should be aware of each other, while BCC is used when the recipients should remain anonymous to each other. This can be useful when sending newsletters, updates, or notifications to a group of users without revealing their email addresses to each other.

$to = 'recipient1@example.com';
$cc = 'ccrecipient@example.com';
$bcc = 'bccrecipient@example.com';
$subject = 'Subject of the email';
$message = 'This is the message content of the email';

$headers = "From: sender@example.com\r\n";
$headers .= "Cc: $cc\r\n";
$headers .= "Bcc: $bcc\r\n";

mail($to, $subject, $message, $headers);