reliable user browser detection with php

There are several ways to detect a user's browser using PHP. One common method is to use the $_SERVER['HTTP_USER_AGENT'] variable, which contains information about the user's browser, such as its name and version.

You can use regular expressions to match this string against known patterns for different browsers. To fake the $_SERVER['HTTP_USER_AGENT'] variable in the example, you can simply assign a custom string to the $user_agent variable before running the code:

Example of reliable user browser detection with PHP

<?php
// in reality you would do $user_agent = $_SERVER['HTTP_USER_AGENT'];
$user_agent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.82 Safari/537.36";

$browser = "Unknown browser";

// Note: Check Chrome before Safari, as Chrome UAs contain "Safari" at the end.
// Simple regex matching is fragile and may produce false positives.
if (preg_match('/MSIE/i', $user_agent)) {
  $browser = 'Internet Explorer';
} elseif (preg_match('/Firefox/i', $user_agent)) {
  $browser = 'Mozilla Firefox';
} elseif (preg_match('/Chrome/i', $user_agent)) {
  $browser = 'Google Chrome';
} elseif (preg_match('/Safari/i', $user_agent)) {
  $browser = 'Apple Safari';
} elseif (preg_match('/Opera/i', $user_agent)) {
  $browser = 'Opera';
}

echo "Your browser is: " . $browser;
?>

Another way is to use the get_browser() function, which uses a browscap.ini file to match the user agent string. This method is more reliable than using regular expressions, but it requires the browscap extension to be enabled and the browscap.ini file to be up-to-date. Note that get_browser() is deprecated as of PHP 8.1.

Example of reliable user browser detection with get_browser() function in PHP

<?php

$browser = get_browser(null, true);
print_r($browser);

It is important to keep in mind that browser detection based on user agent strings is not 100% reliable, as the string can be easily spoofed or customized by the user. For production applications, modern approaches like feature detection or User-Agent Client Hints are strongly recommended.