我只是想使用当前页面上其他页面的输入来显示用户键入的内容。但是，输入所来自的整个页面却出现在该页面上，就像一个iframe。 我尝试了include并把需求一次放在了首位，但这没用。
这是第2页（student.php）
<html>
<head lang='de'>
<title>Admin User Verwaltung</title>
<meta charset='UTF-8'>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">
</head>
<body>
<div class="container-fluid">
<!-- Header -->
<div class="row" id="header">
<div class="col-md-3">
<img src="logo.png" id="logo">
</div>
<div class="col-md-6">
<h1 id="heading">Benutzeroberfläche User</h1>
</div>
<div class="col-md-3">
<p id="profile">
<?php
require_once ('log_in.php');
echo $_POST['user_name'];
?>
</p>
</div>
</div>
</div>
</body>
那是第1页（log_in.php）
<form method="POST" action="log_in.php" accept-charset="UTF-8" class="">
<!-- <input name="_token" type="hidden" value="Ca3dsumBPuWvCa7tJ13oK6khcG6HVhfY1X9bxQhK"> -->
<div class="form-group">
<label>User Name</label>
<input class="form-control" tabindex="1" required="true" placeholder="z.B. User001" autofocus="true" name="username" type="text">
</div>
<div class="form-group">
<label class="d-flex">Passwort
<a class="ml-auto" href="https://studentenportal.fhws.de/password-reset">Passwort vergessen?</a>
</label>
<div class="input-group">
<input id="password" class="form-control" tabindex="2" required="true" name="password" type="password" placeholder="6 bis 15 zeichen">
</div>
</div>
<!--angemeldet bleiben-->
<div class="form-group">
<div class="custom-control custom-checkbox">
<input type="checkbox" class="custom-control-input" name="remember" tabindex="3" value="1" id="remember">
<label class="custom-control-label" for="remember">Angemeldet bleiben</label>
</div>
</div>
<button type="submit" class="btn btn-primary" tabindex="4">Anmelden</button>
</form>