您好，我正在尝试将用户ID和密码发送到PHP文件，并在json中回显它。如果我仅输入一个值时在输入表单标签中“要求”，它将返回带有该值的json，另一个返回为空字符串。但是，如果我同时输入两者，则根本不会进入XMLHttpRequest。 如果我删除“ required”，那么仅输入一个值也不起作用。谢谢！
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>first assignment</title>
<link rel="stylesheet" href="style.css">
<script>
function curlcheck() {
var user_id = document.getElementById("user_id").value;
var pass = document.getElementById("password").value;
var body = "ucid=" + user_id + "&password=" + pass;
xhr = new XMLHttpRequest();
xhr.open("POST", "front_curl.php", true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.onreadystatechange = function() {
if (xhr.status === 200 && xhr.readyState === 4) {
var response_json = JSON.parse(xhr.responseText);
//checks for json and "success" value from it
console.log("in successfull responce");
console.log(response_json.success);
console.log(response_json);
} else {
//checks when status did not come back successful
console.log("status NOT success");
console.log(xhr.responseText);
}
};
xhr.send(body);
}
</script>
</head>
<body>
<div class="somebox"></div>
<ul>
<h3>Team 1 Online Exam System</h3>
</ul>
<form action="" method="POST">
<div name="form header" class="formhead">
<h1>Welcome</h1>
<p><span id="loginerr" class="err_alert"></span></p>
</div>
<div class="login_box">
<lable for="user_id">User ID</lable>
<input type="text" placeholder="Enter User ID" id="user_id" required>
<label for="password">Password</label>
<input type="password" placeholder="Enter Password" id="password" required>
<button id="but" type="submit" onclick="curlcheck()">Login</button>
</div>
</form>
<div class="footer">
</div>
</body>
</html>
