Question

以下代码始终显示错误消息：

注意：未定义的索引：p C：\ xampp \ htdocs \ school \ content.php 在 2 行< 注意：未定义索引：p C：\ xampp \ htdocs \ school \ content.php 2 行< 注意：未定义的索引：p C：\ xampp \ htdocs \ school \ content.php 6

<?php

    if($_GET['p'] == "home" || !$_GET['p']){
        echo "<title>Welcome to Homepage</title>";
    }elseif($_GET['p'] == "about"){
        echo "<title>ABOUT | $schoolname</title>";
    }if($_GET['p'] == "contact"){
        echo "<title>CONTACT US | $schoolname</title>";
    }

?>

我添加了isset，但效果不佳。因为错误消息消失了，但是..

<?php

    if(isset($_GET['p']) and $_GET['p'] == "home" || !isset($_GET['p']) and !$_GET['p'] ){
        echo "<title>Welcome to Homepage</title>";
    }elseif(isset($_GET['p']) and $_GET['p'] == "about"){
        echo "<title>ABOUT | $schoolname</title>";
    }if(isset($_GET['p']) and $_GET['p'] == "contact"){
        echo "<title>CONTACT US | $schoolname</title>";
    }

?>

出现在标题栏中的是 http：// localhost / school .. 我希望这样，如果它在主页上：＆＃34;欢迎来到主页＆＃34;。

... Thaanksss

Answer 1

因为您希望在$_GET['p']=='home'或!isset($_GET['p'])上触发主页，所以您可以这样做：

$title = "Welcome to the Homepage";

if (isset($_GET['p'])) {
    if ($_GET['p'] == "about")
        $title = "About | $schoolname";
    elseif ($_GET['p'] == "contact")
        $title = "CONTACT US | $schoolname";   
}

echo "<title>$title</title>";

这会将默认页面设为主页，并且仅在$_GET['p']设置为about或contact时才会更改

Answer 2

使用OR时要小心，最好用括号条件括起你的术语，但是代码更清晰如下

<?php
    if(isset($_GET['p'])){
      if( $_GET['p'] == "home" ){
          echo "<title>Welcome to Homepage</title>";
      }elseif($_GET['p'] == "about"){
          echo "<title>ABOUT | $schoolname</title>";
      }if( $_GET['p'] == "contact"){
          echo "<title>CONTACT US | $schoolname</title>";
      }
    }else{
         echo "<title>Welcome to Homepage</title>";
    }

?>

或

  <?php
    $message=array("hombe"=>"Welcome to Homepage","about"=>"ABOUT | $schoolname","contact"=>"CONTACT US | $schoolname");
    if(isset($_GET['p'],$message[$_GET['p']])){
           echo "<title>".$message[$_GET['p']]."</title>";
    }else{
         echo "<title>Welcome to Homepage</title>";
    }

?>

Answer 3

<?php
$pgdata = array();
$pgdata['home'] = array(
  'title'=>'Title for Home page',
);
$pgdata['about'] = array(
  'title'=>'Title for About Me page',
);
$pgdata['contact'] = array(
  'title'=>'Title for Contact',
);
$pgname = isset($_GET['pg']) ? trim(strip_tags($_GET['pg'])) : 'home';
$title = $pgdata[$pgname]['title'];
header('Content-type: text/html; charset=utf-8');
?>
<!doctype html>
<html>
<head>
 <meta charset="utf-8" />
 <title><?php echo $title; ?></title>
</style>
</head>
<body>

<header id="header">
 <h1><?php echo $title; ?></h1>
</header>
<section id="posts">
 <nav id="menu">
  <ul>
   <li><a href="home.php" title="Home page">Home</a></li>
   <li><a href="home.php?pg=about" title="About Me">About</a></li>
   <li><a href="home.php?pg=Contact" title="Contact">Contact</a></li>
  </ul>
 </nav>
 </section>
</body>
</html>

Answer 4

使用您的方法，每个新标题都会有一个新的elseif语句。只需将标题存储在数组中或从数据库中获取它们，如下所示：

$titles = [
    'default' => '<title>Welcome to Homepage</title>',
    'about' => "<title>ABOUT | $schoolname</title>",
    'contact' => "<title>CONTACT US | $schoolname</title>",
];

之后，您只需使用以下代码即可显示任何标题：

if (!array_key_exists('p', $_GET) || !array_key_exists($_GET['p'], $titles)){
    echo $titles['default'];
} else {
    echo $titles[$_GET['p']];
}

Answer 5

你的if条件可能不符合你的期望。其他人提供了解决方案，我将向您展示x and y || a and b的结果：此代码

function tt($msg, $b=true) {
  echo 'Call to tt ',$msg,' returning ', ($b)?'True':'False', "\n"; 
  return $b;
 }

if (tt('isset1') and tt('value1') || tt('isset2') and tt('value2')) 
   {echo "Expression is true\n";} else {echo "Expression is false\n";}

结果

Call to tt isset1 returning True
Call to tt value1 returning True
Call to tt value2 returning True
Expression is true

因此跳过or运算符后面的表达式。

如何在PHP中添加isset $ _GET多个函数

5 个答案: