发送邮件是许多站点必备的功能了，尤其是博客网站，发送邮件就更不能缺少了，当有访客在网站上面留下文章评论时，有时候是一个问题，哪么管理员在线进行回复时，同样需要将回复的内容发送到访客邮箱，这样就增加了访客的粘性。

在博客界，我们知道知名的PHP WordPress，需要一个邮件的插件即可进行在线回复邮件，ASP中有ZBLOG，还有一些第三方的评论系统都提供了邮件的发送，比如多说，无觅之类的，都是免费的。

这些功能是怎样实现的呢，PHP中还是比较简单一些的，只需要提供一个邮件的发送类即可以了，所有涉及到的方法都嵌入到这个类里面，哪么在使用的时候只需要实例化这个类即可，下面介绍的这个类便是功能比较强大的发邮件类了，可以应用到任何PHP的站点上，类里面已经给出了实例化的例子，实例化需要自己来配置SMTP服务器帐号和密码，普通使用的是163或QQ之类的邮件发送服务器了，如果还不会配置，可以到163邮件官方去看一下帮助文件。

当然不管是PHP还是ASP在使用邮件发送时，都需要开启邮件服务，否则服务器不支持是无法使用的，ASP相对来说较为麻烦一些，PHP的就简单许多了，基本上LIUNX系统都默认开启了邮件的服务。

下面是PHP发邮件类，可以结合自己的页面进行使用，代码如下：

<?php
class smtp
{
var $smtp_port;
var $time_out;
var $host_name;
var $log_file;
var $relay_host;
var $debug;
var $auth;
var $user;
var $pass;
var $sock;
function smtp($relay_host = "", $smtp_port = 25,$auth = false,$user,$pass)
{
$this->debug = true;
$this->smtp_port = $smtp_port;
$this->relay_host = $relay_host;
$this->time_out = 30;
$this->auth = $auth;
$this->user = $user;
$this->pass = $pass;
$this->host_name = "localhost";
$this->log_file ="";
$this->sock = FALSE;
}
function sendmail($to, $from, $subject = "", $body = "", $mailtype, $cc = "", $bcc = "", $additional_headers = "")
{
$mail_from = $this->get_address($this->strip_comment($from));
$body = ereg_replace("(^|(\r\n))(\\.)", "\\1.\\3", $body);
$header .= "MIME-Version:1.0\r\n";
if($mailtype=="HTML")
{
$header .= "Content-Type:text/html\r\n";
}
$header .= "To: ".$to."\r\n";
if ($cc != "")
{
$header .= "Cc: ".$cc."\r\n";
}
$header .= "From: $from<".$from.">\r\n";
$header .= "Subject: ".$subject."\r\n";
$header .= $additional_headers;
$header .= "Date: ".date("r")."\r\n";
$header .= "X-Mailer:By Redhat (PHP/".phpversion().")\r\n";
list($msec, $sec) = explode(" ", microtime());
$header .= "Message-ID: <".date("YmdHis", $sec).".".($msec*1000000).".".$mail_from.">\r\n";
$TO = explode(",", $this->strip_comment($to));

if ($cc != "") {
$TO = array_merge($TO, explode(",", $this->strip_comment($cc)));
}
if ($bcc != "") {
$TO = array_merge($TO, explode(",", $this->strip_comment($bcc)));
}

$sent = TRUE;
foreach ($TO as $rcpt_to) {
$rcpt_to = $this->get_address($rcpt_to);
if (!$this->smtp_sockopen($rcpt_to)) {
$this->log_write("Error: Cannot send email to ".$rcpt_to."\n");
$sent = FALSE;
continue;
}
if ($this->smtp_send($this->host_name, $mail_from, $rcpt_to, $header, $body)) {
$this->log_write("E-mail has been sent to <".$rcpt_to.">\n");
} else {
$this->log_write("Error: Cannot send email to <".$rcpt_to.">\n");
$sent = FALSE;
}
fclose($this->sock);
$this->log_write("Disconnected from remote host\n");
}
echo "<br>";
echo $header;
return $sent;
}

/* Private Functions */

function smtp_send($helo, $from, $to, $header, $body = "")
{
if (!$this->smtp_putcmd("HELO", $helo)) {
return $this->smtp_error("sending HELO command");
}
#auth
if($this->auth){
if (!$this->smtp_putcmd("AUTH LOGIN", base64_encode($this->user))) {
return $this->smtp_error("sending HELO command");
}

if (!$this->smtp_putcmd("", base64_encode($this->pass))) {
return $this->smtp_error("sending HELO command");
}
}
#
if (!$this->smtp_putcmd("MAIL", "FROM:<".$from.">")) {
return $this->smtp_error("sending MAIL FROM command");
}

if (!$this->smtp_putcmd("RCPT", "TO:<".$to.">")) {
return $this->smtp_error("sending RCPT TO command");
}

if (!$this->smtp_putcmd("DATA")) {
return $this->smtp_error("sending DATA command");
}

if (!$this->smtp_message($header, $body)) {
return $this->smtp_error("sending message");
}

if (!$this->smtp_eom()) {
return $this->smtp_error("sending <CR><LF>.<CR><LF> [EOM]");
}

if (!$this->smtp_putcmd("QUIT")) {
return $this->smtp_error("sending QUIT command");
}

return TRUE;
}

function smtp_sockopen($address)
{
if ($this->relay_host == "") {
return $this->smtp_sockopen_mx($address);
} else {
return $this->smtp_sockopen_relay();
}
}

function smtp_sockopen_relay()
{
$this->log_write("Trying to ".$this->relay_host.":".$this->smtp_port."\n");
$this->sock = @fsockopen($this->relay_host, $this->smtp_port, $errno, $errstr, $this->time_out);
if (!($this->sock && $this->smtp_ok())) {
$this->log_write("Error: Cannot connenct to relay host ".$this->relay_host."\n");
$this->log_write("Error: ".$errstr." (".$errno.")\n");
return FALSE;
}
$this->log_write("Connected to relay host ".$this->relay_host."\n");
return TRUE;;
}

function smtp_sockopen_mx($address)
{
$domain = ereg_replace("^.+@([^@]+)$", "\\1", $address);
if (!@getmxrr($domain, $MXHOSTS)) {
$this->log_write("Error: Cannot resolve MX \"".$domain."\"\n");
return FALSE;
}
foreach ($MXHOSTS as $host) {
$this->log_write("Trying to ".$host.":".$this->smtp_port."\n");
$this->sock = @fsockopen($host, $this->smtp_port, $errno, $errstr, $this->time_out);
if (!($this->sock && $this->smtp_ok())) {
$this->log_write("Warning: Cannot connect to mx host ".$host."\n");
$this->log_write("Error: ".$errstr." (".$errno.")\n");
continue;
}
$this->log_write("Connected to mx host ".$host."\n");
return TRUE;
}
$this->log_write("Error: Cannot connect to any mx hosts (".implode(", ", $MXHOSTS).")\n");
return FALSE;
}

function smtp_message($header, $body)
{
fputs($this->sock, $header."\r\n".$body);
$this->smtp_debug("> ".str_replace("\r\n", "\n"."> ", $header."\n> ".$body."\n> "));

return TRUE;
}

function smtp_eom()
{
fputs($this->sock, "\r\n.\r\n");
$this->smtp_debug(". [EOM]\n");

return $this->smtp_ok();
}

function smtp_ok()
{
$response = str_replace("\r\n", "", fgets($this->sock, 512));
$this->smtp_debug($response."\n");

if (!ereg("^[23]", $response)) {
fputs($this->sock, "QUIT\r\n");
fgets($this->sock, 512);
$this->log_write("Error: Remote host returned \"".$response."\"\n");
return FALSE;
}
return TRUE;
}

function smtp_putcmd($cmd, $arg = "")
{
if ($arg != "") {
if($cmd=="") $cmd = $arg;
else $cmd = $cmd." ".$arg;
}

fputs($this->sock, $cmd."\r\n");
$this->smtp_debug("> ".$cmd."\n");

return $this->smtp_ok();
}

function smtp_error($string)
{
$this->log_write("Error: Error occurred while ".$string.".\n");
return FALSE;
}

function log_write($message)
{
$this->smtp_debug($message);

if ($this->log_file == "") {
return TRUE;
}

$message = date("M d H:i:s ").get_current_user()."[".getmypid()."]: ".$message;
if (!@file_exists($this->log_file) || !($fp = @fopen($this->log_file, "a"))) {
$this->smtp_debug("Warning: Cannot open log file \"".$this->log_file."\"\n");
return FALSE;
}
flock($fp, LOCK_EX);
fputs($fp, $message);
fclose($fp);

return TRUE;
}

function strip_comment($address)
{
$comment = "\\([^()]*\\)";
while (ereg($comment, $address)) {
$address = ereg_replace($comment, "", $address);
}

return $address;
}

function get_address($address)
{
$address = ereg_replace("([ \t\r\n])+", "", $address);
$address = ereg_replace("^.*<(.+)>.*$", "\\1", $address);

return $address;
}

function smtp_debug($message)
{
if ($this->debug) {
echo $message."<br>";
}
}

function get_attach_type($image_tag) { //

$filedata = array();

$img_file_con=fopen($image_tag,"r");
unset($image_data);
while ($tem_buffer=AddSlashes(fread($img_file_con,filesize($image_tag))))
$image_data.=$tem_buffer;
fclose($img_file_con);

$filedata['context'] = $image_data;
$filedata['filename']= basename($image_tag);
$extension=substr($image_tag,strrpos($image_tag,"."),strlen($image_tag)-strrpos($image_tag,"."));
switch($extension){
case ".gif":
$filedata['type'] = "image/gif";
break;
case ".gz":
$filedata['type'] = "application/x-gzip";
break;
case ".htm":
$filedata['type'] = "text/html";
break;
case ".html":
$filedata['type'] = "text/html";
break;
case ".jpg":
$filedata['type'] = "image/jpeg";
break;
case ".tar":
$filedata['type'] = "application/x-tar";
break;
case ".txt":
$filedata['type'] = "text/plain";
break;
case ".zip":
$filedata['type'] = "application/zip";
break;
default:
$filedata['type'] = "application/octet-stream";
break;
}
return $filedata;
}
}
?>

<?php

$smtpserver = "smtp.163.com";//SMTP服务器
$smtpserverport =25;//SMTP服务器端口
$smtpusermail = "caowlong163@163.com";//SMTP服务器的用户邮箱
$smtpemailto = "caowlong@qq.com";//发送给谁
$smtpuser = "caowlong163@163.com";//SMTP服务器的用户帐号
$smtppass = "XXX";//SMTP服务器的用户密码
$mailsubject = "PHP100测试邮件系统";//邮件主题
$mailbody = "<h1>你的用户名是张三，密码是11111 </h1>";//邮件内容
$mailtype = "HTML";//邮件格式（HTML/TXT）,TXT为文本邮件
$smtp = new smtp($smtpserver,$smtpserverport,true,$smtpuser,$smtppass);
$smtp->debug = true;//是否显示发送的调试信息
$smtp->sendmail($smtpemailto, $smtpusermail, $mailsubject, $mailbody, $mailtype);
?>