How can PHP developers ensure proper character encoding for special characters like "ü" in their output?

When outputting special characters like "ü" in PHP, developers should ensure that the correct character encoding is set to UTF-8 to display these characters properly. This can be done by setting the content type header to UTF-8 and using functions like htmlentities() or htmlspecialchars() to encode special characters before outputting them.

header('Content-Type: text/html; charset=UTF-8');
$specialCharacter = "ü";
echo htmlentities($specialCharacter, ENT_QUOTES, 'UTF-8');