如何使用php来实现给前端返回json数据

数据库中查询返回json

[
    {"id":"1","address":"China"},
    {"id":"2","address":"美国"}

]

php代码：

<?php    

header('Content-Type:application/json');  //此声明非常重要

    try {        

    $conn = new PDO("mysql:host=localhost;dbname=orig", 'admin', 'admin');        

    $conn -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);        

    $conn->exec("SET NAMES utf8");   //设置编码

    } catch(PDOException $e) {

        echo "conn_error:
" . $e -> getMessage();

    }    $sql = "select id,address from ip_segments limit 2;";    

    $result = $conn->query($sql)->fetchAll(PDO::FETCH_ASSOC);

 

    echo json_encode($result,JSON_UNESCAPED_UNICODE);  //JSON_UNESCAPED_UNICODE防止中文乱码

    ?>

返回多个字段的json格式

{

    "total":2,

    "rows":[

        {"id":"1","address":"IANA"},

        {"id":"2","address":"美国"}

    ]}

php代码写法：

<?php

    header('Content-Type:application/json');    

    try {        

    $conn = new PDO("mysql:host=localhost;dbname=orig", 'admin', 'admin');        

    $conn -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);        

    $conn->exec("SET NAMES utf8");

    } catch(PDOException $e) {        

    echo "conn_error:
" . $e -> getMessage();

    }    

    $sql = "select id,address from ip_segments limit 2;";    

    $result = $conn->query($sql)->fetchAll(PDO::FETCH_ASSOC);    

    $json['total'] = count($result);    

    $json['rows'] = $result;    

    echo json_encode($json,JSON_UNESCAPED_UNICODE);

    ?>