What are some best practices for implementing browser-specific functionality in PHP based on user agent detection?

When implementing browser-specific functionality in PHP based on user agent detection, it is important to use caution as user agent strings can be easily manipulated. One best practice is to use a library like browscap.ini to accurately detect the user agent. Another approach is to focus on feature detection rather than user agent detection whenever possible. Lastly, consider using browser-specific CSS or JavaScript instead of PHP for simpler and more reliable solutions.

$user_agent = $_SERVER['HTTP_USER_AGENT'];

if(strpos($user_agent, 'Chrome') !== false){
    // Code specific for Chrome browser
} elseif(strpos($user_agent, 'Firefox') !== false){
    // Code specific for Firefox browser
} elseif(strpos($user_agent, 'Safari') !== false){
    // Code specific for Safari browser
} else {
    // Code for other browsers or default behavior
}