案例:PHP案例     状态:不可编辑再运行    进入竖版
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<!DOCTYPE HTML> 
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<html>
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<head>
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<style>
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.error {color: #FF0000;}
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</style>
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</head>
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<body> 
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<?php
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// 定义变量并设置为空值
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$nameErr = $emailErr = $genderErr = $websiteErr = "";
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$name = $email = $gender = $comment = $website = "";
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if ($_SERVER["REQUEST_METHOD"] == "POST") {
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   if (empty($_POST["name"])) {
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     $nameErr = "姓名是必填的";
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   } else {
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     $name = test_input($_POST["name"]);
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     // 检查姓名是否包含字母和空白字符
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     if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
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       $nameErr = "只允许字母和空格"; 
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     }
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   }
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   if (empty($_POST["email"])) {
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     $emailErr = "电邮是必填的";
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   } else {
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     $email = test_input($_POST["email"]);
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     // 检查电子邮件地址语法是否有效
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     if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email)) {
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       $emailErr = "无效的 email 格式"; 
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     }
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   }
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   if (empty($_POST["website"])) {
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     $website = "";
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   } else {
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     $website = test_input($_POST["website"]);
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     // 检查 URL 地址语法是否有效(正则表达式也允许 URL 中的斜杠)
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     if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
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       $websiteErr = "无效的 URL"; 
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     }
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   }
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   if (empty($_POST["comment"])) {
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     $comment = "";