为了提供API接口，我们常常在读取数据库后，将数据转换为数组，通过json_encode转为JSON，即可满足使用需要。现将代码粘帖如下：

1. 读取一条记录，转为数组并输出JSON

include("../../db/conn.php");//数据库连接；
echo "<pre>";
//数据库读取后，直接转换为数组显示;
$sql = "select salesid,fromstore,fromsaler,salestime,salenum,totalprice from midea_sales WHERE salesid=44";
$results = mysqli_query($con, $sql);
$rows = mysqli_fetch_assoc($results);
foreach ($rows as $key => $v) {
	$res[$key] = $v;
}
echo json_encode($res);

2. 读取N条记录，转为多维数组并输出JSON（第一种写法）

//数据库读取后，直接转换为数组显示;
$sql = "select salesid,fromstore,fromsaler,salestime,salenum,totalprice from midea_sales";
$results = mysqli_query($con, $sql);

$data = array();//初始化数组;

class Alteration
{
	public $fromstore;
	public $fromsaler;
	public $salenum;
	public $totalprice;
}

while ($row = mysqli_fetch_assoc($results)) {
	$alter = new Alteration();//实例化对象;
	$alter->fromstore = $row['fromstore'];
	$alter->fromsaler = $row['fromsaler'];
	$alter->salenum = $row['salenum'];
	$alter->totalprice = $row['totalprice'];
	$data[] = $alter;
}
echo json_encode($data);

3. 读取N条记录，转为多维数组并输出JSON（第二种写法）

$sql = "select salesid,fromstore,fromsaler,salestime,salenum,totalprice from midea_sales";
$results = mysqli_query($con, $sql);
while ($rows = mysqli_fetch_assoc($results)) {
	$res[] = $rows;
}
//$res = str_replace('[', '{', json_encode($res));
//$res = str_replace(']', '}', $res);
print_r($res);

4.读取N条记录，转为多维数组并输出JSON（第三种写法），适合获取全部记录

$sql = "select salesid,fromstore,fromsaler,salestime,salenum,totalprice from midea_sales";
$results = mysqli_query($con, $sql);
$rows = mysqli_fetch_all($results);
print_r($rows);

在转换的过程中，JSON格式会出现[]和｛｝两种格式的JSON，而实际应用中对{}的接口是标准接口。如何转换呢？
原因在于：当array是一个从0开始的连续数组时，json_encode出来的结果是一个由[]括起来的字符串；而当array是不从0开始或者不连续的数组时，json_encode出来的结果是一个由{}括起来的key-value模式的字符串。

$sql = "select salesid,fromstore,fromsaler,salestime,salenum,totalprice from midea_sales";
$results = mysqli_query($con, $sql);
$rows = mysqli_fetch_all($results);
$rows = str_replace('[', '{', json_encode($rows));
$rows = str_replace(']', '}', $rows);
echo json_encode($rows);