PHP Program to get the client IP address

An IP address is a unique address(numerical label) that identifies a device on the internet or a local network. IP stands for "Internet Protocol," which is the set of rules governing the format of data sent via the internet or local network.

An IP address serves two principal functions: host or network interface identification and location addressing.

Internet Protocol version 4 (IPv4) defines an IP address as a 32-bit number. However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new version of IP (IPv6), using 128 bits for the IP address, was developed in 1995, and standardized in December 1998. In July 2017, a final definition of the protocol was published. IPv6 deployment has been ongoing since the mid-2000s.

IP addresses are usually written and displayed in human-readable notations, such as 172.16.254.2 in IPv4, and 2001:db8:0:1234:0:567:8:1 in IPv6. The size of the routing prefix of the address is designated in CIDR notation by suffixing the address with the number of significant bits, e.g., 192.168.1.16/24, which is equivalent to the historically used subnet mask 255.255.255.0.

The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries. They are responsible in their designated territories for assignment to end users and local Internet registries, such as Internet service providers. IPv4 addresses have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each. Each ISP or private network administrator assigns an IP address to each device connected to its network.

ALGORITHM

STEP 1: Check if the ip is from share internet, then assign the ip to the variable.

STEP 2: Check if the ip is from proxy, then assign the ip to the variable.

STEP 3: Check if the ip is from remote address, then assign the ip to the variable.

STEP 4: Display the value of the variable.

PHP Source Code

                                          <?php
//whether ip is from share internet
if (!empty($_SERVER['HTTP_CLIENT_IP']))   
  {
    $ip_address = $_SERVER['HTTP_CLIENT_IP'];
  }
//whether ip is from proxy
elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))  
  {
    $ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
  }
//whether ip is from remote address
else
  {
    $ip_address = $_SERVER['REMOTE_ADDR'];
  }
echo $ip_address;
?>
                                      

OUTPUT

192.168.1.120