代码：
<html><?php// PHP - 验证Name、E-mail、以及URL// 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 = "Name is required";} else {$name = test_input($_POST["name"]);// 检查名字是否包含字母和空格if (!preg_match("/^[a-z-A-z]*$/", $name)) {$nameErr = "Only letters and white space allowed";}}if (empty($_POST["email"])) {$emailErr = "Email is requied";// 检查电邮语法是否有效if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/", $email)) {$emailErr = "Invalid email format";}}if (empty($_POST["website"])) {$website = "";} else {$website = test_input($_POST["website"]);// 检查URL地址语言是否有效(此正则表达式同样允许URL中的下划线)if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i", $website)) {$websiteErr = "Invalid URL";}}if (empty($_POST["comment"])) {$comment = "";} else {$comment = test_input($_POST["comment"]);}if (empty($_POST["gender"])) {$genderErr = "Gander is required";} else {$gender = test_input($_POST["gender"]);}}function test_input($data) {$data = trim($data);$data = stripslashes($data);$data = htmlspecialchars($data);return $data;}?><head><title>PHP 表单验证</title></head><body><form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">Name: <input type="text" name="name"><span class="error">* <?php echo $nameErr;?></span><br><br>E-mail:<input type="text" name="email"><span class="error">* <?php echo $emailErr;?></span><br><br>Website:<input type="text" name="website"><span class="error"><?php echo $websiteErr;?></span><br><br><label>Comment: <textarea name="comment" rows="5" cols="40"></textarea><br><br>Gender:<input type="radio" name="gender" value="female">Female<input type="radio" name="gender" value="male">Male<span class="error">* <?php echo $genderErr;?></span><br><br><input type="submit" name="submit" value="Submit"></form></body></html>
回显：
存在问题：等深入了解以后再瞅瞅，现在一直看不出哪里出问题了，正则表达式不是很懂，几乎是照本搬科。
PHP 表单验证
原文地址：https://www.cnblogs.com/xsr7yer/p/9075857.html