PhpForm表单验证

<!DOCTYPE HTML>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<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 = "姓名是必填的";
   } else {
     $name = test_input($_POST["name"]);
     // 检查姓名是否包含字母和空白字符
     if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
       $nameErr = "只允许字母和空格"; 
     }
   }
   
   if (empty($_POST["email"])) {
     $emailErr = "电邮是必填的";
   } else {
     $email = test_input($_POST["email"]);
     // 检查电子邮件地址语法是否有效
     if (!preg_match("/([w-]+@[w-]+.[w-]+)/",$email)) {
       $emailErr = "无效的 email 格式"; 
     }
   }
     
   if (empty($_POST["website"])) {
     $website = "";
   } else {
     $website = test_input($_POST["website"]);
     // 检查 URL 地址语法是否有效（正则表达式也允许 URL 中的斜杠）
     if (!preg_match("/(?:(?:https?|ftp)://|www.)[-a-z0-9+&@#/%?=~_|!:,.;]*[-a-z0-9+&@#/%=~_|]/i",$website)) {
       $websiteErr = "无效的 URL"; 
     }
   }

   if (empty($_POST["comment"])) {
     $comment = "";
   } else {
     $comment = test_input($_POST["comment"]);
   }

   if (empty($_POST["gender"])) {
     $genderErr = "性别是必选的";
   } else {
     $gender = test_input($_POST["gender"]);
   }
}

function test_input($data) {
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
}
?>

    <h2>PHP 验证实例</h2>
    <p>
        <span class="error">* 必需的字段</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> 电邮：<input type="text" name="email"> <span
            class="error">* <?php echo $emailErr;?></span> <br>
        <br> 网址：<input type="text" name="website"> <span
            class="error">
            <?php echo $websiteErr;?>
        </span> <br>
        <br> 评论：
        <textarea name="comment" rows="5" cols="40"></textarea>
        <br>
        <br> 性别： <input type="radio" name="gender" value="female">女性
        <input type="radio" name="gender" value="male">男性 <span
            class="error">* <?php echo $genderErr;?></span> <br>
        <br> <input type="submit" name="submit" value="提交">
    </form>

    <?php
echo "<h2>您的输入：</h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>

</body>
</html>
From:http://www.w3school.com.cn/php/php_form_complete.asp