PHP未定义索引:HTTP_USER_AGENT

Question

以下代码验证访问该站点的用户代理,但是我收到错误.我需要更新哪些内容以适应没有设置用户代理的情况？

错误 PHP注意:未定义的索引:第7行的Utils.php中的HTTP_USER_AGENT

码

public static function detectBrowser()
    {
        $userAgent = strtolower($_SERVER['HTTP_USER_AGENT']);

        if (preg_match('/opera/', $userAgent)) {
            $name = 'opera';
        }
        elseif (preg_match('/webkit/', $userAgent)) {
            $name = 'safari';
        }
        elseif (preg_match('/msie/', $userAgent)) {
            $name = 'msie';
        }
        elseif (preg_match('/mozilla/', $userAgent) && !preg_match('/compatible/', $userAgent)) {
            $name = 'mozilla';
        }
        else {
            $name = 'unrecognized';
        }

        if (preg_match('/.+(?:rv|it|ra|ie)[\/: ]([\d.]+)/', $userAgent, $matches)) {
            $version = $matches[1];
        }
        else {
            $version = 'unknown';
        }

        if (preg_match('/linux/', $userAgent)) {
            $platform = 'linux';
        }
        elseif (preg_match('/macintosh|mac os x/', $userAgent)) {
            $platform = 'mac';
        }
        elseif (preg_match('/windows|win32/', $userAgent)) {
            $platform = 'windows';
        }
        else {
            $platform = 'unrecognized';
        }

        return array(
            'name'      => $name,
            'version'   => $version,
            'platform'  => $platform,
            'userAgent' => $userAgent
        );
    }

Answer 1

User-Agent标头是可选的.防火墙可以过滤它,或者人们可以配置其客户端以省略它.只需检查isset()是否存在即可.或者更好的是,!empty()用作空标题也不会有用:

public static function detectBrowser() {
    if(empty($_SERVER['HTTP_USER_AGENT'])) {
        return array(
            'name' => 'unrecognized',
            'version' => 'unknown',
            'platform' => 'unrecognized',
            'userAgent' => ''
        );
    }

    // your old code here
}

但是,由于您的所有代码似乎在空字符串上工作正常并且还产生"未知"值,您只需更改以下行:

$userAgent = strtolower($_SERVER['HTTP_USER_AGENT']);

像这样:

$userAgent = isset($_SERVER['HTTP_USER_AGENT'])
               ? strtolower($_SERVER['HTTP_USER_AGENT'])
               : '';

Answer 2

使用isset:

if( !isset( $_SERVER['HTTP_USER_AGENT'])){
    $name = "none";
}else{
     $userAgent = strtolower($_SERVER['HTTP_USER_AGENT']);

    if (preg_match('/opera/', $userAgent)) {
        $name = 'opera';
    } [... yourcode ...]
}