PHP Check If A String Contains Something

We can use the PHP built in function strpos to determine if a string contains specific word(s).

For example, we can detect if the IP address of the current user is in the accepted IP list as below:

<?php
	$ip_address = $_SERVER['REMOTE_ADDR'];
 
	$allow_ips = "127.0.0.1;1.54.115.234";
 
	if (strpos($allow_ips, $ip_address) !== FALSE)
		echo 'Okay, pass';
	else
		echo "sorry!";
?>