<?php
/* filename: smtp-client.php
 * Author:      Nick Soracco <nick@deepgroove.org>
 *
 * Description: a VERY simple (and probably not totally RFC 2821 compliant)
 *              smtp client.  This was borne out of frustration that PHP's own
 *              mail() routine always invokes a sendmail binary instead of
 *              using SMTP on *NIX machines.  It was also my attempt at learning
 *              more about PHP's socket library, and rfc 282[1|2].
 *
 * Resources:
 *              http://phpmailer.sourceforge.net
 *              http://www.phpguru.org/static/smtp.html
 *              http://www.faqs.org/rfcs/rfc2821.html
 *              http://www.faqs.org/rfcs/rfc2822.html
 */


/* Returns the 3 digit code from an MTA response */
function get_smtp_code( $string ) {
	return( substr( trim($string) , 0, 3 ) );
}

/* A simple function to connect, unencrypted, to an SMTP server of your choice and then
 * send an email message.  One transaction and message per function call, with an arbitary
 * number of cc's and bcc's, up to your mail server's limits.  (Postfix, around 10000 each.)
 *
 * Please note this function does NOT validate input.  That should be the job of the program
 * driving this function.  So please, check your addresses!
 */
function send_smtp_mail( $server, $to, $from, $subject, $message, $cc = "", $bcc = "", $extra_headers = "" ) {

	//$debug = true;

	/* Since we must wait for replies from the mail server, we'll have to open the socket once,
	 * do a series of fwrite() and fread() calls to handle the headers, then one fwrite() call
	 * for data.
	 */
	$socket = fsockopen( $server, 25, $errno, $errstr, 30 );
	if( !$socket ) {
		echo("Error connecting to $server on port 25.\r\n");
		if($debug) {
			echo("$errstr - ($errno)\n");
		}
		fclose( $socket );
		exit(1);
	}
	$response = fread( $socket, 100 );
	$code = get_smtp_code( $response );
	if( 220 != $code ) {
		echo("No ESMTP response.\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(99);
	}
	
	fwrite( $socket, "HELO pwnzors\r\n" );
	$response = fgets( $socket, 100 );
	if( 250 != get_smtp_code( $response ) ) {
		echo("Failed at HELO stage\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(2);
	}

	fwrite( $socket, "mail from: $from\r\n" );
	$response = fgets( $socket, 100 );
	if( 250 != get_smtp_code( $response ) ) {
		echo("Failed at mail from: $from stage\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(3);
	}

	/* per RFC 2821, each person listed in Bcc: must be RCPT TO:'d, so we
	 * split that string into an array, and then append the $to variable
	 * to the end, thus doing all our rcpt work in one fell swoop.
	 */
	$bccs = split( ",", $bcc );
	$bccs[] = $to;
	if($debug) {
		print_r($bccs);
	}
	foreach( $bccs as $addy ) {
		fwrite( $socket, "rcpt to: " . trim($addy) . "\r\n" );
		$response = fgets( $socket, 100 );
		if( 250 != get_smtp_code( $response ) ) {
			echo("Failed at rcpt to: $addy stage\n");
			if($debug) {
				echo("Server response: $response\n");
			}
			fclose( $socket );
			exit(4);
		}
	}
	
	fwrite( $socket, "data\r\n" );
	$response = fgets( $socket, 80 );
	if( 354 != get_smtp_code( $response ) ) {
		echo("Failed at data stage.\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(5);
	}

	/* writing additional headers.
	 * Do I need the Date: header?  For now, I'm leaving it off, but the RFC2821 format
	 * is gained by passing the format string: "r" to date().  I think most MTA's will
	 * take care of this for you though, Postfix seems to.
	 */
	fwrite( $socket, "From: $from\r\nTo: $to\r\nSubject:$subject\r\n" );

	/* write message */
	fwrite( $socket, $message."\r\n" );

	/* queue and close connection */
	fwrite( $socket, "\r\n.\r\n" );
	$response = fgets( $socket, 80 );
	if( 250 != get_smtp_code( $response ) ) {
		echo("Failed at queuing stage.\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(6);
	}

	fwrite( $socket, "quit\r\n" );
	$response = fgets( $socket, 80 );
	if( 221 != get_smtp_code( $response ) ) {
		echo("Failed at quitting stage.\n");
		if($debug) {
			echo("Server response: $response\n");
		}
		fclose( $socket );
		exit(7);
	}

	fclose( $socket );
	return true;
}
?>