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<!DOCTYPE html>
<html>
<body>
<?php
// Variable to check
$ip = "2001:0db8:85a3:08d3:1319:8a2e:0370:7334";
// Validate ip as IPv6
if (!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) === false) {
  echo("$ip is a valid IPv6 address");
} else {
  echo("$ip is not a valid IPv6 address");
}
?>
</body>
</html>
2001:0db8:85a3:08d3:1319:8a2e:0370:7334 is a valid IPv6 address