php - 如何通过php从mysql数据库中获取所有产品类别并返回json数组

Question

我有一个安卓应用。 我想向 get_categories.php 文件发送获取请求。 在我想要的 get_categories.php 文件中

$query_categories        = "SELECT category_name FROM categories";

并将在该表中找到的所有类别返回到 json 数组中。

我该怎么做？

这是我的不完整代码:

if (!empty($_GET)) {


    $query_categories        = "SELECT category_name FROM categories";
    $success = false;

    try{
        $sth = $connection->prepare($query_categories);
        //$sth->execute(array(':user_id' => $user_id));
        //$user_items_count = $sth->rowCount();  - these are lines from other php file I've used 

        foreach($)//??

        $success = true;
    } catch (PDOException $ex) {

        $response["success"] = 0;
        $response["message"] = $ex;
        die(json_encode($response));
        $connection = null;
    }

    if($success) {
        $response["success"] = 1;
        $response["message"] = "Kylie";

        die(json_encode($response));
        $connection = null;      

    } else {
        $response["success"] = 2;
        $response["message"] = "something went wrong";
        die(json_encode($response));
        $connection = null;
    }

} else {
        $response["success"] = 3;
        $response["message"] = "Another brick in the wall";   
        echo json_encode($response);
        $connection = null;
}

稍后，在我的 Java 代码中，我如何对其进行解码？ 通常到目前为止，在我的其他 JSON 传输中，我收到了没有数组的普通 Json 对象并以这种方式读取它们:

setUserLastSeen(json.getString(TAG_USER_LAST_SEEN)); //for example.

但是我如何解码一个数组呢？

Answer 1

对于 php 端，这是如何获取类别数组并生成 json，对于准备好的语句，这是如何完成的

$success = false;
try {

  $DBH = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
$success = true;
}
catch(PDOException $e) {
$response["success"] = 0;
$response["message"] = 'Connection failed: ' . $e->getMessage();
$response["data"]=null;
die(json_encode($response));
}

$query_categories = "SELECT category_name FROM categories";

try{

$sth = $sth->prepare($query_categories );
$success = true;

} catch(PDOException $e) {
$response["success"] = 0;
$response["message"] = 'Prepare failed: ' . $e->getMessage();
$response["data"]=null;
die(json_encode($response));
}

try{
$sth->execute();
$success = true;
} catch(PDOException $e) {
$response["success"] = 0;
$response["message"] = 'Execute failed: ' . $e->getMessage();
$response["data"]=null;
die(json_encode($response));
}

$categories = $sth->fetchAll(PDO::FETCH_COLUMN, 0);/* fetches all categories from db */

/* Output of $query_categories
Array
(
    [0] => cat1
    [1] => cat2
    [2] => cat3
    [3] => cat4
)
*/
/* json encode $query_categories 
["cat1","cat2","cat3","cat4"]
*/

/* check if categories exist or not*/
if(empty($categories)){
        $response["success"] = 0;
        $response["message"] = "No categories found";
        $response["data"]=null;
        die(json_encode($response));
        $connection = null; 

}

if($success) {
    $response["success"] = 1;
    $response["message"] = "Kylie";
    $response["data"]=$categories;
    die(json_encode($response));
    $connection = null;      
 /* output
 {"success":0,"message":"Kylie","data":["cat1","cat2","cat3","cat4"]}
 */
} else {
    $response["success"] = 2;/* don't where you are setting success to 2*/
    $response["message"] = "something went wrong";
    $response["data"]=null;
    die(json_encode($response));
    $connection = null;
}

} else {
        $response["success"] = 3;/* don't where you are setting success to 3*/
        $response["message"] = "Another brick in the wall";  
        $response["data"]=null; 
        die(json_encode($response));
        $connection = null;
}

我不擅长 java 但这里有引用 How to parse a JSON and turn its values into an Array?

/* store json string in  the_json */
JSONObject myjson = new JSONObject(the_json);
JSONArray the_json_array = myjson.getJSONArray("data");

Note: make sure on java side you must check the success from json which must be ==1 and the_json_array is not null

PHP Data Objects