What is the recommended method to determine the screen resolution of users in PHP?

To determine the screen resolution of users in PHP, you can use the `$_SERVER['HTTP_USER_AGENT']` variable to get the user's browser information and then parse the user agent string to extract the screen resolution. This can be done by searching for specific keywords like 'Screen' or 'Resolution' in the user agent string. Additionally, you can use JavaScript to get the screen resolution and pass it to PHP through AJAX. 

$user_agent = $_SERVER['HTTP_USER_AGENT'];

if (preg_match('/\bScreen\b.*\bResolution\b\s*([0-9]+x[0-9]+)/i', $user_agent, $matches)) {
    $screen_resolution = $matches[1];
    echo "User's screen resolution is: " . $screen_resolution;
} else {
    echo "Unable to determine user's screen resolution.";
}

Keywords

screen resolution user agent get_browser $_SERVER viewport dimensions

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