In the context of PHP email functionality, what are some key functions and constructs to be aware of when manipulating and formatting data for transmission?

When manipulating and formatting data for transmission in PHP email functionality, it is important to be aware of key functions such as `mail()` for sending emails, `htmlspecialchars()` for encoding special characters in the email body, and `wordwrap()` for formatting the email content to fit within specified line lengths. Additionally, constructs like headers for setting email headers and attachments for including files in the email should also be considered.

// Example code snippet for sending an email with formatted data
$to = "recipient@example.com";
$subject = "Test Email";
$message = "This is a test email with formatted data.";
$message = wordwrap($message, 70); // wrap text at 70 characters per line
$headers = "From: sender@example.com\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n"; // specify content type and character encoding
mail($to, $subject, $message, $headers);