x
 
<!DOCTYPE HTML>  
<html>
<head>
<style>
.error {color: #FF0000;}
</style>
</head>
<body>  
<?php
// 定义变量并设置为空值
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  if (empty($_POST["name"])) {
    $nameErr = "姓名是必填项";
  } else {
    $name = test_input($_POST["name"]);
  }
  
  if (empty($_POST["email"])) {
    $emailErr = "邮箱是必填项";
  } else {
    $email = test_input($_POST["email"]);
  }
    
  if (empty($_POST["website"])) {
    $website = "";
  } else {
    $website = test_input($_POST["website"]);
  }
  if (empty($_POST["comment"])) {
    $comment = "";
  } else {
    $comment = test_input($_POST["comment"]);
  }
  if (empty($_POST["gender"])) {
    $genderErr = "性别是必填项";
  } else {
    $gender = test_input($_POST["gender"]);
  }
}
function test_input($data) {
  $data = trim($data);
  $data = stripslashes($data);
  $data = htmlspecialchars($data);
  return $data;
}
?>
<h2>PHP 表单验证示例</h2>
<p><span class="error">* 必填字段</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">  
  姓名: <input type="text" name="name">
  <span class="error">* <?php echo $nameErr;?></span>
  <br><br>
  邮箱: <input type="text" name="email">
  <span class="error">* <?php echo $emailErr;?></span>
  <br><br>
  网站: <input type="text" name="website">
  <span class="error"><?php echo $websiteErr;?></span>
  <br><br>
  评论: <textarea name="comment" rows="5" cols="40">


性别: *

您的输入:"; echo $name; echo "
"; echo $email; echo "
"; echo $website; echo "
"; echo $comment; echo "
"; echo $gender; ?>