Combining multiple strpos() in an if () statement - php

Question

I'm trying to make added user agent stay on a page. If user agent is not detected, then redirect.
This code works
$useragent = $_SERVER['HTTP_USER_AGENT'];
if (strpos($useragent, "useragent") === false) {
header("Location: http://google.com/");
}
So I tried to add multiple user agent like this but didn't work.
$useragent = $_SERVER['HTTP_USER_AGENT'];
if (
strpos($useragent, "agent1") === false ||
strpos($useragent, "agent2") === false ||
strpos($useragent, "agent2") === false
) {
header("Location: http://google.com/");
}

Answer 1

You may want a code that is simpler to update than your successive strpos(). Also, you should search case-insensitively. And firing the PCRE engine at each page access may not be optimal.
So I would keep the stripos() approach like this:
<?php
$partial_allowed_UA_names = ['mozilla', 'chrome', 'safari']; # <----- Config here.
$go_away = true;
foreach ($partial_allowed_UA_names as $v) {
if (stripos($_SERVER['HTTP_USER_AGENT'], $v) !== false) {
$go_away = false;
break;
}
}
if ($go_away) header('Location: https://www.google.com/');
?>
Best regards

Answer 2

You can use preg_match() instead.
$useragent = $_SERVER['HTTP_USER_AGENT'];
$agents = ['agent1', 'agent2', 'agent3']; //array of predefined names of agents
if (!preg_match('/' . implode('|', $agents) . '/i', $useragent)) { //check if current user agent is not enlisted
header("Location: http://google.com/");
}