PHP 检测访问设备是移动端还是PC端

$userAgent = $_SERVER['HTTP_USER_AGENT'];
$devices = array(
  "iPhone" => "(iPhone)",
  "Android" => "(Android)",
  "Windows Phone" => "(Windows Phone)",
  "iPad" => "(iPad)"
);

$deviceType = "PC";

foreach ($devices as $device => $regexp) {
  if (preg_match("/" . $regexp . "/i", $userAgent)) {
    $deviceType = $device;
    break;
  }
}

if ($deviceType === "PC") {
  // PC端代码
} else {
  // 移动端代码
}