How should the mail() function be properly used in PHP to ensure that the required arguments are correctly formatted and passed?

When using the mail() function in PHP, it is important to ensure that the required arguments are correctly formatted and passed. This includes providing the recipient email address, subject, message body, and any additional headers in the correct format. Failure to do so may result in the email not being sent or being marked as spam. To properly use the mail() function, make sure to format the arguments as specified in the PHP documentation and handle any errors that may occur during the sending process.

$to = 'recipient@example.com';
$subject = 'Test Email';
$message = 'This is a test email.';
$headers = 'From: sender@example.com' . "\r\n" .
    'Reply-To: sender@example.com' . "\r\n" .
    'X-Mailer: PHP/' . phpversion();

if(mail($to, $subject, $message, $headers)) {
    echo 'Email sent successfully.';
} else {
    echo 'Failed to send email.';
}