我已经成功地使用 php 创建了一个联系表单，它提供了各种所需的消息。现在我想添加一个简单的随机算术验证码（非图像）。请参阅下面的匿名（工作）html 表单和现有（工作，但没有算术验证码）php。
这个想法是以与其他错误消息相同的方式显示“不正确的答案”，或者传递到Thankyou页面以获得正确填写的正确答案的表格。我在这方面做得很好，但不能让它发挥作用。非常感谢任何帮助。
HTML：
<p>Area of interest:
<input type="radio" name="likeit" value="A" checked="checked" /> A
<input type="radio" name="likeit" value="B" /> B
<input type="radio" name="likeit" value="C" /> C</p>
<p>How did you hear about us?
<select name="how">
<option value=""> -- Please select -- </option>
<option>Recommendation</option>
<option>Internet</option>
<option>Advertisement</option>
<option>Other</option>
</select></p>
<p><strong>Your message subject:</strong><br /><input type="text" name="subject" size="35"/></p>
<p><strong>Your message:</strong><br />
<textarea name="comments" rows="10" cols="40"></textarea></p>
<p>Please answer the following arithmetic question: What is <?php echo $digit1;?> + <?php echo $digit2;?>?
<input name="captcha" type="text" size="2" id="captcha"/></p>
<p><input type="submit" value="Send" /></p>
</form>
PHP：
<?php
/* Contact form with arithmetic captcha */
$myemail = "enquiries@X.co.uk";
/* Check all form inputs using check_input function */
$yourname = check_input($_POST['yourname'], "Enter your name");
$email = check_input($_POST['email']);
$telephone = check_input($_POST['telephone']);
$website = check_input($_POST['website']);
$likeit = check_input($_POST['likeit']);
$how_find = check_input($_POST['how']);
$subject = check_input($_POST['subject'], "Add a subject");
$comments = check_input($_POST['comments'], "Add your message");
/* If e-mail is not valid show error message */
if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/", $email))
{
show_error("Email address is not valid");
}
/* If URL is not valid set $website to empty */
if (!preg_match("/^(https?:\/\/+[\w\-]+\.[\w\-]+)/i", $website))
{
$website = '';
}
/* Message for the email */
$message = "Hello!
Your contact form has been submitted by:
Name: $yourname
Email: $email
Telephone: $telephone
URL: $website
Area of interest? $likeit
How did they find us? $how_find
Comments:
$comments
End of message
";
/* Send the message using mail() function */
mail($myemail, $subject, $message);
/* Redirect visitor to the thankyou page */
header('Location: thankyou.html');
exit();
/* Functions used */
function check_input($data, $problem='')
{
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
if ($problem && strlen($data) == 0)
{
show_error($problem);
}
return $data;
}
function show_error($myError)
{
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!--
Head data in here
-->
<html xmlns="http://www.w3.org/1999/xhtml">
<body>
<div id="mainheader">
<div id="mainlogo">
<h1><a href="http://www.X.co.uk/" title="X">
<img style="border:0;width: 260px; height: 160px;" src="images/X.jpg" alt="X" /></a></h1>
</div>
</div>
<div id="content">
<div class="content">
<h2 class="title">Error!</h2>
<p><strong>Please correct the following error:</strong></p>
<p><?php echo $myError; ?></p>
</div>
</div>
<div id="panel">
<div id="main" class="boxed">
<h2 class="heading">Main</h2>
<ul>
<li><a href="index.html">Home</a> </li>
<li><a href="about.html">About</a> </li>
<li><a href="contact.html">Contact</a> </li>
</ul>
</div>
<div id="services" class="boxed">
<h2 class="heading">Services</h2>
<ul>
<li><a href="services.html">Services</a> </li>
<li><a href="recent-projects.html">Recent projects</a> </li>
</ul>
</div>
<div id="pricing" class="boxed">
<h2 class="heading">Pricing</h2>
<ul>
<li><a href="pricing.html">Pricing</a> </li>
</ul>
</div>
<div id="info" class="boxed">
<h2 class="heading">Info</h2>
<ul>
<li><a href="tips-and-tricks.html">Tips and tricks</a> </li>
<li><a href="useful-links.html">Useful links</a> </li>
<li><a href="faq.html">Frequently asked questions</a> </li>
<li><a href="site-map.html">Site map</a> </li>
</ul>
</div>
<div id="contact" class="boxed">
<h2 class="heading">Contact</h2>
<ul>
<li><a href= "mailto:enquiries&#64;X.co.uk">Contact by email</a> </li>
<li><strong>Telephone:<br />X</strong> </li>
</ul>
</div>
</div>
<div id="mainfooter">
<p> &#169; 2011 X<br />Designed by <a href="http://www.X.co.uk/" title="X"><strong>X</strong></a> </p>
<a href="http://validator.w3.org/check?uri=referer" title="Valid XHTML 1.0">
<img style="border:0;width:88px;height:31px" src="images/valid-xhtml10.png" alt="Valid XHTML 1.0" />
</a>
<a href="http://jigsaw.w3.org/css-validator/check/referer" title="Valid CSS!">
<img style="border:0;width:88px;height:31px" src="images/vcss.gif" alt="Valid CSS!" />
</a>
</div>
</body>
</html>
<?php
exit();
}
?>