Php code summary for prohibiting access from a single IP address and ip address segment

Someone asked me on the internet how to disable ip access in php. through tests, I found that the following code is good and the principle is relatively simple.
// Add IP address access restrictions
If (getenv ('http _ CLIENT_IP ') & strcasecmp (getenv ('http _ CLIENT_IP'), 'Unknown ')){
$ Userip = getenv ('http _ CLIENT_IP ');
} Elseif (getenv ('http _ X_FORWARDED_FOR ') & strcasecmp (getenv ('http _ X_FORWARDED_FOR'), 'Unknown ')){
$ Userip = getenv ('http _ X_FORWARDED_FOR ');
} Elseif (getenv ('remote _ ADDR ') & strcasecmp (getenv ('remote _ ADDR'), 'Unknown ')){
$ Userip = getenv ('remote _ ADDR ');
} Elseif (isset ($ _ SERVER ['remote _ ADDR ']) & $ _ SERVER ['remote _ ADDR '] & strcasecmp ($ _ SERVER ['remote _ ADDR'], 'Unknown ')){
$ Userip = $ _ SERVER ['remote _ ADDR '];
}
$ Banned_ip = array (
"127.0.0.1 ",
"203.0.0.1 ",
"56.12.50.65 ",
"192.168.1.88"
);
If (in_array ($ userip, $ banned_ip ))
{
Die ("Your IP is block to connect! ");
}
Echo "script home test ";
?>
Disable IP segments

The code is as follows:

// Add IP address access restrictions
If (getenv ('http _ CLIENT_IP ') & strcasecmp (getenv ('http _ CLIENT_IP'), 'Unknown ')){
$ Userip = getenv ('http _ CLIENT_IP ');
} Elseif (getenv ('http _ X_FORWARDED_FOR ') & strcasecmp (getenv ('http _ X_FORWARDED_FOR'), 'Unknown ')){
$ Userip = getenv ('http _ X_FORWARDED_FOR ');
} Elseif (getenv ('remote _ ADDR ') & strcasecmp (getenv ('remote _ ADDR'), 'Unknown ')){
$ Userip = getenv ('remote _ ADDR ');
} Elseif (isset ($ _ SERVER ['remote _ ADDR ']) & $ _ SERVER ['remote _ ADDR '] & strcasecmp ($ _ SERVER ['remote _ ADDR'], 'Unknown ')){
$ Userip = $ _ SERVER ['remote _ ADDR '];
}
$ Ban_range_low = ip2long ("217.0.0.0"); // on the ip address segment
$ Ban_range_up = ip2long ("217.00000000255"); // ip end
$ Ip = ip2long ($ userip]);
If ($ ip> $ ban_range_low & $ ip <$ ban_range_up)
{
Print "Banned ";
Exit ();
}
?>