How can checking the HTTP header Content-Type and meta charset tags help resolve Umlaut display issues in PHP?

Umlaut display issues in PHP can be resolved by ensuring that the HTTP header Content-Type and meta charset tags are correctly set to UTF-8 encoding. This ensures that special characters like Umlauts are displayed properly on the webpage.

header('Content-Type: text/html; charset=utf-8');
echo '<meta http-equiv="Content-Type" content="text/html; charset=utf-8">';