当用户提交表单时，做到以下两件事是非常有必要：
使用 PHP trim() 函数去除用户输入数据中不必要的字符 (如：空格，tab，换行)。
使用PHP stripslashes()函数去除用户输入数据中的反斜杠 (\)
<!DOCTYPE HTML> <html><head></head><body> <?php// define variables and set to empty values$name = $email = $gender = $comment = $website = "";if ($_SERVER["REQUEST_METHOD"] == "POST"){ $name = test_input($_POST["name"]); $email = test_input($_POST["email"]); $website = test_input($_POST["website"]); $comment = test_input($_POST["comment"]); $gender = test_input($_POST["gender"]);}function test_input($data){ $data = trim($data); $data = stripslashes($data); $data = htmlspecialchars($data); return $data;}?><h2>PHP Form Validation Example</h2><form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>"> Name: <input type="text" name="name"> <br><br> E-mail: <input type="text" name="email"> <br><br> Website: <input type="text" name="website"> <br><br> 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 <br><br> <input type="submit" name="submit" value="Submit"> </form><?phpecho "<h2>Your Input:</h2>";echo $name;echo "<br>";echo $email;echo "<br>";echo $website;echo "<br>";echo $comment;echo "<br>";echo $gender;?></body></html>
