How can a client (PC) be uniquely identified for program access using PHP?

One way to uniquely identify a client (PC) for program access using PHP is by generating a unique identifier based on the client's IP address and user agent string. This combination can create a fingerprint that is unique to each client accessing the program. 

$client_id = md5($_SERVER['REMOTE_ADDR'] . $_SERVER['HTTP_USER_AGENT']);
echo $client_id;

Keywords

client identification unique identifier PHP session HTTP cookies user agent

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