php连接数据库出现问题

$conn = mysqli_connect($servername,$username,$password);
if ($conn) {
// $conn->query("SET NAMES 'UTF8'");
mysqli_select_db($conn,$dbname);

$search = "select check_num FROM check where check_num ='".$_POST["number"]."'";

  $result = mysqli_query($conn,$search);
  $datarow = mysqli_num_rows($result);
    $arr = array();
    if($datarow>0){
       //     $content = json_encode($_SESSION['username']);
       //  if($f  = file_put_contents($file, $content,FILE_APPEND)){// 这个函数支持版本(PHP 5)
       // //echo "写入成功。<br />";
      // }

      for($i = 0;$i < $datarow ; $i++){
        $search_arr = mysqli_fetch_assoc($result);
        $number = $search_arr['check_num'];
        $password = $sreach_arr['check_pass']; 
      }

       $arr['result'] = 1 ;
       $arr['data'] = $password;

    }else{
           $arr['result'] = 0;
           $arr['data'] = '验证码输入错误';
         }

    echo json_encode($arr);
}
 $conn->close();
 ?>
    三个问题
    1.   Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in G:\Wamp\wamp\www\electricmobile\check.php on line 27
    2. Notice: Undefined index: number in G:\Wamp\wamp\www\electricmobile\check.php on line 24
    3. Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in G:\Wamp\wamp\www\electricmobile\check.php on line
    这是什么情况 为什么我一用mysqli_num_rows 就出错

你数据库链接错了，少了dbname

$password = $sreach_arr['check_pass']; 这行变量名也写错了

$result = mysqli_query($search,$conn); sql语句放前面吧