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Accepted
Pavlo B.
Asked: 2020-11-10 01:42:14 +0800 CST 2020-11-10 01:42:14 +0800 CST

标头错误 - 警告：无法修改标头信息 - 标头已发送

  • 772

这是错误：

警告：无法修改标头信息 - 标头已由第 16 行 C:\xampp\htdocs\newop\mainindex.php 中的（输出开始于 C:\xampp\htdocs\newop\template\header.php:80）发送

标题的第 80 行是这样的（它是单行，仅解包）：

<div class="col-md-2 col-xs-2 device-select">
    <a href="budget.php?device=2">
        <img class="full-width" src="res/images/device2.jpg">
        </img>
    </a>
    <center class="popular-devices">
<?php echo $lang['header_dropdown_string_2'];?>
    </center>
</div>

...这是代码：

<?php
session_start();
if (!isset($_SESSION['user'])){ header("Location: index.php"); }
?>
<html>
  <body>
<?php
  include("template/head.php");
  include("template/header.php");
  include ("db_files/db.php");
  $usermail = mysqli_real_escape_string($db, $_SESSION['user']);
  $strSQL = "SELECT nivel FROM usuarios where email ='$usermail'";
  $query = mysqli_query($db, $strSQL);
  while ($result = mysqli_fetch_array($query)){
    if ($result['nivel'] == 1 || $result['nivel'] == 2){
    header("location: userlist:php");
  }
  
}
  $state = array(
    1 => $lang['state_name_string_1'],
    2 => $lang['state_name_string_2'],
    3 => $lang['state_name_string_3'],
    4 => $lang['state_name_string_4'],
  );
?>
  <div class="content container">
    <div class="row no-margin no-padding">
      <div class="col-md-2 hidden-sm hidden-xs">
        <div class="mainuserimage">
          <img class="full-width" src="res/images/users/user1.png"/>
        </div>
        <div>
<?php
            $strSQL = "SELECT nombre, email, telefono FROM usuarios where email ='$usermail'";
            $query = mysqli_query($db, $strSQL);
            while ($result = mysqli_fetch_array($query)){
              echo "<i class='glyphicon glyphicon-user'></i> ".$result['nombre']."<br>";
              echo "<i class='glyphicon glyphicon-envelope'></i> ".$result['email']."<br>";
              echo "<i class='glyphicon glyphicon-earphone'></i> ".$result['telefono']."<br>";
            }
?>
        </div>
      </div>
      <div class="col-md-10 col-xs-12">
      <h3 class="main-title"><?php echo $lang['mainindex_string_1']; ?></h3><br>
        <div class="row">
          <div class="col-md-2 col-xs-3">
            <p><?php echo $lang['mainindex_string_2']; ?></p>
          </div>
          <div class="col-md-2 col-xs-3">
            <p><?php echo $lang['mainindex_string_3']; ?></p>
          </div>
          <div class="col-md-2 col-xs-3">
            <p><?php echo $lang['mainindex_string_4']; ?></p>
          </div>
          <div class="col-md-2 hidden-sm hidden-xs">
            <p><?php echo $lang['mainindex_string_5']; ?></p>
          </div>
          <div class="col-md-2 col-xs-3">
            <p><?php echo $lang['mainindex_string_6']; ?></p>
          </div>
          <div class="col-md-2 hidden-sm hidden-xs">
            <p><?php echo $lang['mainindex_string_7']; ?></p>
          </div>
<?php
            $strSQL = "SELECT id, marca, modelo, imei, descripcion_problema, problem, problem2, problem2_namees, estado, fecha_creacion FROM tickets, problem2 WHERE tickets.email = '$usermail' AND tickets.problem2 = problem2.problem2_id";
            $query = mysqli_query($db, $strSQL);
            while($result = mysqli_fetch_array($query)){ ?>
              <div class="col-md-2 col-xs-3">
                <p><a href="repairdetail.php?id=<?php echo $result['id']; ?>"><i class="glyphicon glyphicon-list-alt"></i></a>  <?php echo $result['marca']; ?></p>
              </div>
              <div class="col-md-2 col-xs-3">
                <p><?php echo $result['modelo']; ?></p>
              </div>
              <div class="col-md-2 col-xs-3">
                <p><?php echo $result['imei']; ?></p>
              </div>
              <div class="col-md-2 hidden-sm hidden-xs">
                <p><?php echo $result['problem2_namees']; ?></p>
              </div>
              <div class="col-md-2 col-xs-3">
                <p><?php echo $state[$result['estado']]; ?></p>
              </div>
              <div class="col-md-2 hidden-sm hidden-xs">
                <p><?php echo $result['fecha_creacion']; ?></p>
              </div>
<?php
            }
?>
          </div>
        </div>
    </div>
  </div>
<?php
  include("template/footer.php");
?>
  </body>
</html>

php

2 Answers

  1. Best Answer

    移动方块：

    include ("db_files/db.php");
$usermail = mysqli_real_escape_string($db, $_SESSION['user']);
$strSQL = "SELECT nivel FROM usuarios where email ='$usermail'";
$query = mysqli_query($db, $strSQL);

while ($result = mysqli_fetch_array($query)){
    if ($result['nivel'] == 1 || $result['nivel'] == 2){
        header("location: userlist.php"); //<= Error: userlist:php !!!
    }
}

    之前：

    <html>
...

    发送或修改 HTTP 标头的 PHP 函数必须在请求的页面开始发送给用户之前执行。

    有关错误的其他信息： - headers already sent

    一条消息HTTP由一个标头Header和一个正文组成Body，它们按此顺序发送到客户端Client。发送时，Body无法再发送Header。

    header()如果您在发送后尝试调用该函数HTML，您将得到著名的错误：Cannot modify header information - headers already sent.

    不仅header()函数修改Header了以下函数：

    在发送之前也会产生错误的其他示例Header：

    • 打开前的空格_<?php
    • 关闭后的空格?>_
    • 将UTF-8 与 BOM 一起使用
    • 显示/添加信息/内容或错误消息：
      HTML, echo, print, var_dump()....etc

    错误代码示例：

    <?php
echo "Foo Bar"; // Mostrar contenido echo
setcookie("Foo", "Bar");

     <?php // Espacio antes del "<?php"
session_start();
?>

    <html> <!-- Mostrando contenido HTML -->
<head>
<?php
session_start();
?>
    • 13

  2. 发生错误是因为您在修改标头之前发送了 html 输出，因此默认标头已经发送。

    您可以通过在 header 命令之后移动 html 块来解决此问题。或者也使用ob_start()第一行代码中的函数。这将启动输出缓冲区缓存，并且在脚本完成之前不会发送标头。

    • 4