PHP はクロスドメインの問題を解決します

<?php
// 制定允许其他域名访问
header("Access-Control-Allow-Origin:*");
// 响应类型
header(&#39;Access-Control-Allow-Methods:POST&#39;);
// 响应头设置
header(&#39;Access-Control-Allow-Headers:x-requested-with, content-type&#39;);
 
//$callback = isset($_REQUEST[&#39;callback&#39;]) ? trim($_REQUEST[&#39;callback&#39;]) : &#39;&#39;; //jsonp回调参数，必需
function getKey($key,$default=""){
    return trim(isset($_REQUEST[$key])?$_REQUEST[$key]:$default);
}
$id = getKey("id");
$conn = mysqli_connect("localhost","root","","test") or die("连接失败");
$conn->query("set names utf8");
$sql = "select * from data where ".$id." is not null";
$result = $conn->query($sql);
$arr = [];
while($row=$result->fetch_assoc()){
    array_push($arr,json_encode($row));
}
$json = json_encode($arr);  //json 数据
print_r($json);