PHP User Authentication by IP Address

In this article, you will learn how to authenticate a user by IP address using PHP programming language.

If you want to restrict the website or page to certain IP addresses, it might be on the grounds that you have an inner system that has a freely perceptible webpage. You may wish to have certain pages visible only to a specific machine on the inner system, or you may want to restrict the page to some static IP address. You can easily do it by reading this article.

This process works by determining the IP address of the user. Suppose you want to allow the website access to IP addresses in the range of 123.121.0.1 to 123.121.0.255. In the given example, we have defined an array of the allowed IP addresses that can view the page. For this, we have taken three array elements. The array("123", "121", "0") limits the users who can view the page to those with an IP address in the range of 123.121.0.1 to 123.121.0.255. The current user's IP address is taken by using a global variable '$_SERVER' and stored in a variable '$REMOTE_ADDR'.

<?php
	$allowed_ip = array("123", "121", "0");
	$REMOTE_ADDR = $_SERVER["REMOTE_ADDR"];
	$remote_ip = explode(".", $REMOTE_ADDR);
	$permitted = 1;
	for($i = 0; $i < sizeof($allowed_ip); $i++) {
		if($remote_ip[$i] != $allowed_ip[$i]) {
			$permitted = 0;
		}
	}
	if($permitted == 1) {
		echo 'Welcome, You are authorized to access this page.';
	}
	else{
		echo 'Access Denied';
	}
?>

In the above example, replace the $allowed_ip array values with your allowed IP address. If you want to restrict the page to only one IP address, then pass all four values of IP address as four elements in the $allowed_ip array.

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