How can PHP be used to decode special characters like umlauts in HTML text?

Special characters like umlauts in HTML text can be decoded using PHP's built-in function `html_entity_decode()`. This function converts HTML entities like ä back to their corresponding characters (in this case, ä). To decode special characters in HTML text, you can simply pass the text through `html_entity_decode()`.

$html_text = "Überprüfen Sie Ihren Text.";
$decoded_text = html_entity_decode($html_text);
echo $decoded_text;