从PHP使用JavaScript更改HTML属性
[英]Change HTML attribute with JavaScript from PHP
问题描述
I have this two HTML elements which are hidden and should become visible when someones enters wrong credentials. 
我有这两个HTML元素，它们是隐藏的，当有人输入错误的凭据时应该可以看到它们。
Username : 用户名 ：
<div class="alert alert-danger login_alert" id="username_alert" role="alert"><span>Your username is incorrect. Please try again.</span></div>
Password : 密码 ：
<div class="alert alert-danger login_alert" id="password_alert" role="alert"><span>Your password is incorrect. Please try again.</span></div>
In php, when a password is wrong, I try this line: 在php中，当密码错误时，我尝试以下行：
echo '<script>console.log("Error: Password incorrect"); document.getElementById(password_alert).style.display = "block";</script>';
This console.log is displayed in the console, but after that I get: 该console.log显示在控制台中，但之后我得到：
Uncaught ReferenceError: password_alert is not defined
at login.php:15
This while password_alert is defined in my div . 这在我的div定义了password_alert 。 I also tried this using ClassName() by creating two login_alert classes for both username and password, but that isn't working either. 我还使用ClassName()通过为用户名和密码创建两个login_alert类来尝试此操作，但这都不起作用。
2 个解决方案
解决方案1
2 2018-10-24 20:07:50
解决方案2
1 2018-10-25 07:52:10
按照@RobinZigmond的建议，通过将整个PHP部分移到HTML <body>的末尾来解决此问题。
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