get_ip.php

function get_ip( $ipaddress = null ) {
		if ( ! empty( $ipaddress ) ) {
			if ( false === WP_Http::is_ip_address( $ipaddress ) ) {
				return '0.0.0.0';
			}

			return $ipaddress;
		}
		$ipaddress = '0.0.0.0';
		if ( getenv( 'HTTP_CF_CONNECTING_IP' ) ) {
			$ipaddress = getenv( 'HTTP_CLIENT_IP' );
		} elseif ( getenv( 'HTTP_CLIENT_IP' ) ) {
			$ipaddress = getenv( 'HTTP_CLIENT_IP' );
		} elseif ( getenv( 'HTTP_X_FORWARDED_FOR' ) ) {
			$ipaddress = getenv( 'HTTP_X_FORWARDED_FOR' );
		} elseif ( getenv( 'HTTP_X_FORWARDED' ) ) {
			$ipaddress = getenv( 'HTTP_X_FORWARDED' );
		} elseif ( getenv( 'HTTP_FORWARDED_FOR' ) ) {
			$ipaddress = getenv( 'HTTP_FORWARDED_FOR' );
		} elseif ( getenv( 'HTTP_FORWARDED' ) ) {
			$ipaddress = getenv( 'HTTP_FORWARDED' );
		} elseif ( getenv( 'REMOTE_ADDR' ) ) {
			$ipaddress = getenv( 'REMOTE_ADDR' );
		}
		// sanitize IP address
		if ( false === WP_Http::is_ip_address( $ipaddress ) ) {
			$ipaddress = '0.0.0.0';
		}

		return $ipaddress;
	}