未定义的索引但可以回显

Question

我尝试从JS（客户端）向PHP（服务器端）发送数据username。问题是我的PHP中有notice undefined index : username，但我可以回显数据。这是我的代码：

JS

function showdatabase(){

   var username =localStorage.getItem('username');  
 //document.write(username);

 if (window.XMLHttpRequest) {
     // code for IE7+, Firefox, Chrome, Opera, Safari
     xmlhttp=new XMLHttpRequest();   } else { // code for IE6, IE5
     xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");   }   xmlhttp.onreadystatechange=function() {
     if (xmlhttp.readyState==4 && xmlhttp.status==200) {
       document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
     }   }

    xmlhttp.open("GET","dataquery.php?username="+username,true);  
    xmlhttp.send(); 
}

PHP

<?php

include('connection.php');


$username=$_GET['username']; echo $username;

//query of database
$result =mysqli_query($mysqlConnection,"SELECT * FROM users WHERE user_ID LIKE '$username'");

echo "<table border='4'>  <tr>    <th> Full Name</th>     </tr>";

//read data from array from database.
while ($row = mysqli_fetch_assoc($result)) {
    echo "<tr>"; echo "<td>".$row['nama_penuh']."</td>"; echo "</tr>"; }
?>

我是编程新手，希望大家都能提供帮助。提前谢谢你：）

Answer 1

您需要在函数username的参数中添加showdatabase，以便：

showdatabase(username) {

   // ** Content of your function **//

}

当您调用您的函数时，需要初始化用户名：

<a href="javascript: showdatabase('John');">MyCall</a>