What are common issues beginners face when trying to send emails using PHP, especially when including multiple variables with line breaks?

Beginners often face issues when sending emails using PHP, especially when including multiple variables with line breaks. One common problem is that line breaks in the email content can break the formatting or structure of the email. To solve this, you can use the PHP `nl2br()` function to convert newline characters to HTML line breaks before sending the email.

$email_content = "Hello " . $username . ",\n\n";
$email_content .= "Thank you for signing up!\n\n";
$email_content .= "Regards,\nYour Website Team";

// Convert newline characters to HTML line breaks
$email_content = nl2br($email_content);

// Send email with the formatted content
mail($to, $subject, $email_content, $headers);