警告：mysqli_num_rows（）はパラメータ1がmysqli_result、booleanは

Question

と予想しています。地区名を選択する際に表示される人の詳細なPHPコードです。

<?php 
define('HOST','localhost'); 
define('USER','root'); 
define('PASS',''); 
define('DB','farmer'); 
$conn = mysqli_connect(HOST,USER,PASS,DB); 

if(!$conn) { 
     //required post params is missing 
     $response["error"] = TRUE; 
     $response["error_msg"] = "Connection could not be established!"; 
     echo json_encode($response); 
    } 
    $sql = "select code,name,mobile from reg_farmer where dist_name=$_POST[dt_name]"; 
    $res = mysqli_query($conn,$sql); 
$num_rows = mysqli_num_rows($res); 
///echo "$num_rows Rows\n"; 
    if ($num_rows == 0){ 
         $response["error"] = TRUE; 
         $response["error_msg"] = "No Data Exist"; 
         echo json_encode($response); 
         exit(0); 
       } 

$result = array(); 
while($row = mysqli_fetch_array($res)){ 
    $result = array("error" => FALSE); 
$b[]=array('code'=>$row[0],'name'=>$row[1],'mobile'=>$row[2]); 
$result["District"] = $b; 
} 
echo json_encode($result); 
mysqli_close($conn); 
?> 

しかし、それは{ "エラー" "いいえデータが存在"：真、 "ERROR_MSGを"}示しマイテーブル構造が

Answer 1

POST dt_nameの下に表示

...変数に格納し、それをmysqlクエリで使用します：$ dt_name = $ _POST ['dt_name'];

この

<?php 
define('HOST','localhost'); 
define('USER','root'); 
define('PASS',''); 
define('DB','test'); 
$conn = mysqli_connect(HOST,USER,PASS,DB); 

if(!$conn) 
{ 
    //required post params is missing 
    $response["error"] = TRUE; 
    $response["error_msg"] = "Connection could not be established!"; 
    echo json_encode($response); 
} 

$dt_name = $_POST['dt_name']; 
$sql = "select code,name,mobile from reg_farmer where dist_name='$dt_name'"; 
$res = mysqli_query($conn,$sql); 

$num_rows = mysqli_num_rows($res); 
//echo "$num_rows Rows\n"; 
if ($num_rows == 0){ 
    $response["error"] = TRUE; 
    $response["error_msg"] = "No Data Exist"; 
    echo json_encode($response); 
    exit(0); 
} 

$result = array(); 
while($row = mysqli_fetch_array($res)){ 
    $result = array("error" => FALSE); 
    $b[]=array('code'=>$row[0],'name'=>$row[1],'mobile'=>$row[2]); 
    $result["District"] = $b; 
} 
echo json_encode($result); 
mysqli_close($conn); 
?>