What is the best way to block IP addresses on a server using PHP?

To block IP addresses on a server using PHP, you can create a function that checks the visitor's IP address against a list of blocked IPs and then denies access if there is a match. This can be implemented by storing the blocked IPs in an array or database and comparing the visitor's IP address against this list before allowing access to the website.

function blockIP($blockedIPs, $visitorIP) {
    if (in_array($visitorIP, $blockedIPs)) {
        header("HTTP/1.1 403 Forbidden");
        exit;
    }
}

$blockedIPs = array("192.168.0.1", "10.0.0.1");
$visitorIP = $_SERVER['REMOTE_ADDR'];

blockIP($blockedIPs, $visitorIP);