Ho utilizzato questa istruzione:

<?php
$headers = apache_request_headers();

foreach ($headers as $header => $value) {
echo "$header: $value <br />\n";
}
?>


Ho ricevuto risultati diversi con Firefox e con Chrome:

Cookie: PHPSESSID=b774aelnkusu0c8thd0abgjmv8
Sec-Gpc: 1
Sec-Fetch-User: ?1
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Sec-Fetch-Dest: document
Upgrade-Insecure-Requests: 1
Accept-Encoding: gzip, deflate, br
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106.0
Connection: close
X-Accel-Internal: /internal-nginx-static-location
X-Real-Ip: 81.208.11.32
Host: sviluppo.enigma3.it


Cookie: PHPSESSID=c86dfmtn9fqr4mcj3aftc7v72r; _gid=GA1.2.972631575.1666357652; _ga=GA1.1.453557358.1599055199; _ga_RP97K6FEVG=GS1.1.1666357651.6.1.1666357858.0.0 .0
Accept-Language: it-IT,it;q=0.9,en-US;q=0.8,en;q=0.7
Accept-Encoding: gzip, deflate, br
Sec-Fetch-Dest: document
Sec-Fetch-User: ?1
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: cross-site
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36
Upgrade-Insecure-Requests: 1
Sec-Ch-Ua-Platform: "Windows"
Sec-Ch-Ua-Mobile: ?0
Sec-Ch-Ua: "Chromium";v="106", "Google Chrome";v="106", "Not;A=Brand";v="99"
Cache-Control: max-age=0
Connection: close
X-Accel-Internal: /internal-nginx-static-location
X-Real-Ip: 81.208.11.32
Host: sviluppo.enigma3.it


Quindi con Chrome (e con Edge) riesco a intercettare la lingua di default del browser, mentre con Firefox no.

Perch� firefox si comporta cos�?