原生php链接数据库，进行数据库的增删改查，并且返回json

1.连接数据库进行多条数据的查询

<?php
header('Content-Type:application/json; charset=utf-8');
header("Access-Control-Allow-Origin: *"); // 允许任意域名发起的跨域请求  
header('Access-Control-Allow-Headers: X-Requested-With,X_Requested_With'); 
$dbhost = 'localhost';  // mysql服务器主机地址
$dbuser = 'root';            // mysql用户名
$dbpass = '';          // mysql用户名密码
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
    die('连接失败: ' . mysqli_error($conn));
}
// 设置编码，防止中文乱码
mysqli_query($conn , "set names utf8");
 $index = $_POST['id'];
 
$sql = 'SELECT  id,typeid,title,click,pubdate,litpic FROM dede_archives where typeid = '.$index;
 
mysqli_select_db( $conn, 'kepuyizhan' );
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
    die('无法读取数据: ' . mysqli_error($conn));
}
$arr = array();
while($row = mysqli_fetch_array($retval, MYSQLI_ASSOC))
{
    array_push($arr,$row);
}
echo  json_encode($arr);
mysqli_close($conn);
?>

2.单条查询

<?php
header('Content-Type:application/json; charset=utf-8');
header("Access-Control-Allow-Origin: *"); // 允许任意域名发起的跨域请求  
header('Access-Control-Allow-Headers: X-Requested-With,X_Requested_With'); 
$dbhost = 'localhost';  // mysql服务器主机地址
$dbuser = 'root';            // mysql用户名
$dbpass = '';          // mysql用户名密码
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
    die('连接失败: ' . mysqli_error($conn));
}
// 设置编码，防止中文乱码
mysqli_query($conn , "set names utf8");
 $index = $_POST['id'];

$sql = 'SELECT body FROM dede_addonarticle where aid = '.$index;
 
mysqli_select_db( $conn, 'kepuyizhan' );
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
    die('无法读取数据: ' . mysqli_error($conn));
}
$arr = array();
while($row = mysqli_fetch_array($retval, MYSQLI_ASSOC))
{
    array_push($arr,$row);
    

}
echo  json_encode($arr);
mysqli_close($conn);
?>