从要在函数中使用的类创建的对象打印出意外的“新”（T_NEW）

Im trying to create a class that I can request to return a variable based on some mobile detection. Im trying to avoid defining anything with global. I'm getting the following error: Parse error: syntax error, unexpected 'new' (T_NEW)

<?php
require_once 'lib/Mobile_Detect.php';

class detectDevice {
  private static $detect = new Mobile_Detect;
  private static $deviceType;

  public static function returnDevice(){

    if ( $detect->isMobile() ) {
      $deviceType = "IS MOBILE";
    }
    if( $detect->isTablet() ){
      $deviceType = "IS TABLET";
    }

    print self::$deviceType;
  }
}

echo detectDevice::returnDevice();
?>

Any suggestions?