在任何输入数据的地方都需要考虑到安全问题，之前我们聊到 php 表单发送邮件的示例，只是简单的介绍了该功能的实行，在实际运用中我们还需要增加一些防护措施，代码如下：
<html>
<body>
<?php
function spamcheck($field)
{
//filter_var() sanitizes the e-mail
//address using FILTER_SANITIZE_EMAIL
$field=filter_var($field, FILTER_SANITIZE_EMAIL);
//filter_var() validates the e-mail
//address using FILTER_VALIDATE_EMAIL
if(filter_var($field, FILTER_VALIDATE_EMAIL))
{
return TRUE;
}
else
{
return FALSE;
}
}
if (isset($_REQUEST['email']))
{//if "email" is filled out, proceed
//check if the email address is invalid
$mailcheck = spamcheck($_REQUEST['email']);
if ($mailcheck==FALSE)
{
echo "Invalid input";
}
else
{//send email
$email = $_REQUEST['email'] ;
$subject = $_REQUEST['subject'] ;
$message = $_REQUEST['message'] ;
mail("someone@example.com", "Subject: $subject",
$message, "From: $email" );
echo "Thank you for using our mail form";
}
}
else
{//if "email" is not filled out, display the form
echo "<form method='post' action=''>
Email: <input name='email' type='text' /><br />
Subject: <input name='subject' type='text' /><br />
Message:<br />
<textarea name='message' rows='15' cols='40'>
</textarea><br />
<input type='submit' />
</form>";
}
?>
</body>
</html>在上面的代码中，我们使用了 PHP 过滤器来对输入进行验证：
FILTER_SANITIZE_EMAIL 从字符串中删除电子邮件的非法字符
FILTER_VALIDATE_EMAIL 验证电子邮件地址
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