How can PHP developers handle character encoding issues, such as displaying special characters like ß, ü, ö, ä correctly in email content when using PHP for sending emails?

PHP developers can handle character encoding issues by ensuring that the correct character encoding is set for the email content. They can use PHP's mb_internal_encoding() function to set the character encoding to UTF-8, which supports special characters like ß, ü, ö, ä. Additionally, developers can use the mb_send_mail() function to send emails with proper encoding.

// Set the character encoding to UTF-8
mb_internal_encoding('UTF-8');

// Send email with proper encoding
$to = 'recipient@example.com';
$subject = 'Subject with special characters: ß, ü, ö, ä';
$message = 'Email content with special characters: ß, ü, ö, ä';
$headers = 'From: sender@example.com' . "\r\n" .
    'Content-Type: text/html; charset=UTF-8' . "\r\n";

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