Zend PHP Certification Study Guide- P8

Managing Email Introduction Terms You’ll Need to Understand n sendmail wrapper n Headers n MIME encoding n SMTPWindows only n smtp_portWindows only n sendmail_fromWindows only n sendmail

Also, certain time formats can befuddle strtotime() For example, this code will cause $tsto be set to -1, indicating an error:

$ts = strtotime(“Fri, 9 Jan 2004 03:26:23 +0000 GMT”);

strtotime()has become confused because two separate time zone offsets (+0000and

GMT) were both specified If you are manually constructing all the inputs to strtotime()

(for example, to take advantage of the next week/last weekfunctionality) this is not

an issue, as you can test your inputs to make sure that they are all correctly handled However, if you are using strtotime()to handle arbitrarily formatted date entries (for example, submitted free form through a web page), you should take into account the possibility of both incomprehensible and improperly interpreted dates

One of the best aspects of strtotime()is using it to handle leap years and daylight saving time If you need to find the time stamp for the current time tomorrow, you can-not simply look 24 hours in the future, as it might be 23 or 25 hours if you cross a day-light saving time boundary.strtotime()takes this into account, though; so to find a this time tomorrow, you could just say

$tomorrow = strtotime(“tomorrow”)

Because you did not specify a time,strtotime()uses the current value

Exam Prep Questions

1 Which of the following sentences are incorrect?

A date()returns the current UNIX datestamp

B date()returns a formatted date string

C date()requires a time stamp to be passed to it

D date()returns a date array

The correct answers are A, C, and D.date()takes a format string and an optional time stamp and produces a formatted date string If a UNIX time stamp is not passed into date(), it will use the current time

2 The function will return the current UNIX time stamp

The correct answer is time()

3 Which of the following functions will output the current time as 11:26 pm?

A print date(‘H:m a’);

B print date(‘G:M a’);

C print date(‘G:i a’);

D print strftime(‘%I:%M %p’);

The correct answers are C and D.

125 Exam Prep Questions

4 The PHP date functions are only guaranteed to work for dates after _

A January 1, 1970 00:00:00

B January 1, 1900 00:00:00

C January 1, 1963 00:00:00

D January 18, 2038 22:14:07

The correct answer is A.The UNIX epoch is January 1, 1970 00:00:00 UTC On

32-bit systems, the date functions are only guaranteed to work until January 19, 2038

5 Internally PHP handles dates and times as

A A ‘date array’ array consisting of the year, month, day, hour, minute, and second

B A UNIX time stamp representing the number of seconds since the UNIX epoch

C An ISO-8601 date entity

D A UNIX time stamp consisting of the number of microseconds since the UNIX epoch

The correct answer is B PHP stores all its dates internally as UNIX time stamps,

which are defined as the number of seconds since the UNIX epoch, January 1,

1970 00:00:00 UTC

Managing Email

Introduction

Terms You’ll Need to Understand

n sendmail wrapper

n Headers

n MIME encoding

n SMTP(Windows only)

n smtp_port(Windows only)

n sendmail_from(Windows only)

n sendmail_path

Techniques You’ll Need to Master

n Mail functions

n URL functions

How Email Is Delivered

If you are going to be writing and deploying PHP scripts that generate and send email messages, you need to know something about how email gets delivered around the Internet.This will help you better understand and support your customers when prob-lems arise Figure 8.1 shows the main components of the email architecture

Figure 8.1 How email is delivered.

Here are the standard terms that you will come across at some point or another

MTA—Mail Transport Agent

When email is sent from organization to organization, it is sent from email server to email server.The software that runs on your email server and handles sending and

receiving email from around the Internet is called the Mail Transport Agent (MTA for

short) Examples of Mail Transport Agents are

n sendmail

n postfix

n qmail

n Microsoft Exchange

n Lotus Notes Mail transport agents talk to each other using the SMTP network protocol

SMTP—Simple Mail Transport Protocol

The Simple Mail Transport Protocol (SMTP) is the standard network-layer protocol for

transmitting an email message across the Internet

Servers normally listen for incoming SMTP connections on port 25

MX Records

When an MTA has an email message to send to another MTA, it has to convert the address in the To:, Cc:, or Bcc: line into an IP address Everything after the @ sign in the

address is taken to be the email domain.This is normally something such as @php.net

Sends email via SMTP May authenticate via SASL Receives email via IMAP or POP3

Mail Server (runs MTA)

DNS Server (provides MX records)

Requests MX records via DNS

Sends email via SMTP

Personal Computer (runs MUA)

Sends email via SMTP May authenticate via SASL Receives email via IMAP or POP3 Mail Server

(runs MTA)

DNS Server (provides MX records)

Requests MX records via DNS

Personal Computer (runs MUA)

Resolves hostnames via DNS

129 How Email Is Delivered

The email domain isn’t the real name of a server It looks like a real name (and has to follow the same rules), but it isn’t It’s actually a special kind of DNS alias

To receive email for your email domain, you have to add an MX record for that email domain to your DNS server

Note

If you don’t set up an MX record in your DNS server, the MTA will look for a matching A record instead.

MUA—Mail User Agent

The Mail User Agent (MUA) is the jargon name for an email client.

Examples of Mail User Agents are

n Outlook Express

n Evolution

n KMail

n pine

n mutt

n Hotmail

A PHP script that sends email is also a type of Mail User Agent

Mail User Agents read email directly from files on disk, via network protocols such as POP3 or IMAP, or via proprietary network protocols (as used by Microsoft Exchange)

Mail User Agents normally send their email by connecting to a Mail Transport Agent over the network via the SMTP network protocol Some UNIX-based Mail User Agents

might send their email instead by executing a sendmail wrapper program.

When a Mail User Agent connects to an MTA via SMTP to send email, it might use SASL to authenticate the user

SASL—Simple Authentication and Security Layer

The Simple Authentication and Security Layer (SASL) is a tried and trusted way to bolt

user-authentication onto existing network protocols SMTP has been extended (via the SMTP AUTH command) to support SASL

If an MTA has been configured to require authentication, only MUAs with built-in support for the SMTP AUTH command will be able to connect to send email

Other Emerging Technologies

Although email is as old as the Internet itself, the rise of unsolicited bulk email

(com-monly called spam), the increasing number of modern viruses that transmit themselves

via email, and the fraudulent use of genuine email addresses for criminal intent mean that we are at the start of a period of great change in how email will be delivered in the future

Junk email filters have become very popular.They can be added both to the MTA and/or the MUA It’s a fair bet that most of the email that these filters mark as ‘junk’ never gets read by a human Junk email filters aren’t perfect; genuine email that looks very like real junk email will also get marked as junk.When you roll out a PHP applica-tion that sends email, you should perform some tests with your customer to make sure that your email will get past whatever junk email filter your customer uses

Because of repeated security holes in MUAs, the more tech-savvy businesses and users

do not accept delivery of HTML email It’s very tempting to send HTML email—such emails look so much nicer than plain-text email.You should ensure that any PHP appli-cation you write that sends email always gives the user the option to choose between plain-text email and HTML email.You should never only support HTML email

If you write and sell PHP software that works with email, it’s important that you keep abreast of the new technologies that are always coming out.When capturing require-ments from your customer, always make sure that you’ve agreed what email technologies the customer has adopted—or is planning to adopt within six months of the end of your project.The customer will (somewhat naively) expect your PHP application to work perfectly with whatever changes he plans to make to his email infrastructure—and will blame you if it doesn’t

Preparing PHP

Before you can send email from your PHP script, you must first ensure that your copy of PHP has been correctly configured

If You Are Using PHP on UNIX

To send email from a PHP script running on UNIX, you must have a sendmail-compatible MTA installed on the same server that your PHP script runs on

On UNIX systems, PHP sends email by running the command-line program

sendmail.sendmailis the de facto standard MTA for UNIX systems

If you are using an alternative to sendmail, it must provide a sendmail wrapper A

sendmail wrapper is a drop-in replacement for the sendmailcommand-line program It must accept the -tand -icommand-line switches at the very least

When PHP is compiled, the configurescript searches for the sendmailcommand in

/usr/bin:/usr/sbin:/usr/etc:/etc:/usr/ucblib:/usr/lib

If configurecannot find the sendmailcommand, then sendmail support will be per-manently disabled.The following PHP functions will either be missing entirely, or will always return an error:

n mail()—will be missing

n ezmlm_hash()—will be missing

n mb_send_mail()—will always return false

131 Preparing PHP

When this happens, you must install a sendmail wrapper, and then recompile PHP

Once PHP is compiled with sendmail support enabled, whenever your script sends email, PHP will use the sendmailcommand discovered by the configurescript If you ever need to override this default, set the sendmail_pathin php.inito point to the

sendmailcommand that you want PHP to use

sendmail_path = ‘/usr/local/bin/sendmail’

If You Are Using PHP on Windows or Netware

Although not documented in the PHP Manual, if you set the sendmail_pathsetting in your php.inifile, PHP will attempt to send email via the sendmail_wrapper—behaving exactly as if PHP were running on UNIX.This can catch you out, so remember to look for it when troubleshooting email problems

If you do not have a sendmail wrapper available, PHP on Windows talks to the mail transport agent (MTA) directly via the SMTP network protocol PHP needs to be con-figured to tell it where to find your MTA:

n The SMTPsetting in php.inimust be set to the hostname (or IP address) of the email server that your MTA is running on.The default value is localhost.You will probably want to change that

n The smtp_portsetting in php.inimust be set to the port that your MTA is lis-tening on.The default value is 25.You probably will not need to change that

Note

It isn’t documented in the PHP Manual, but PHP on Novell Netware uses the same code for email support as PHP on Windows.

Caution

It is currently not possible to get PHP on UNIX to talk directly to the MTA via SMTP.

PHP on Windows does not support SASL If your MTA is configured to require authen-tication, you will need to change the security on your MTA to enable PHP to send emails through successfully

On UNIX, the MTA will automatically say that the email is from whichever user your PHP script is running as

This can’t be done on Windows because PHP is connecting to the MTA over the network via SMTP Instead, PHP will work out who the email is from by looking in these places in this order:

n the from:header line passed to the mail()function

n the sendmail_fromsetting in the php.inifile

PHP will display an error and refuse to send the email if it cannot determine who the email is from

If you compile your own version of PHP on Windows, and you are going to use it to send emails, it’s important that you build PHP with the Perl-compatible regular expres-sion (PCRE) library included PHP on Windows relies on the PCRE functions to make sure that headers have the correct end of line character If you build PHP on Windows without PCRE support, you might find that MTAs refuse to accept your emails for delivery

With PHP correctly configured, you can now send email from your PHP scripts

Sending Email

Use the PHP function mail()to send an email message from a PHP script

The first parameter of the mail()function is the email address to send the email message to

Assuming that you are running your PHP script on the server that is the MTA for the example.com email domain, and that there is a local user called fred, all of these are valid email addresses:

n fred

The MTA thinks you are trying to send an email to the local user fred

n fred@example.com

This is the normal form for an email address, and the one that you are probably most familiar with

n fred @ example.com

The MTA will automatically collapse the whitespace in the email address

Although perfectly legal, email addresses with whitespace are seldom seen today

n “Fred Bloggs” <fred@example.com>

The MTA will automatically extract the fred@example.comfrom between the angular brackets

The entire string will be added as is to the From: line of the email message Note that the double quotes are important—do not leave them out

Sending an Email to More Than One Recipient

Add additional addresses to the toparameter Separate them by a comma and a space:

fred, joe@example.com, “Jane Doe” <jane.doe@example.com>

If you want to cc: or bcc: an email to someone, do this by adding additional headers to your email

133 Formatting an Email Message

Managing Email Headers

Email headers are lines of text that go at the start of an email message Headers hold information used by MTAs and MUAs If you pass a list of additional headers into the

mail()function, it will automatically add these headers to your email message Each header in the list must be separated by \r\n

The Cc: and Bcc: Headers

The Cc: and Bcc: headers allow you to send a copy of an email message to other people

All recipients will be able to see the list of addresses in the To: and Cc: lines of the email, but will not be able to see the list of addresses in the Bcc: line

The Cc: and Bcc: headers are optional If you provide either of them (or both of them), they must follow the same rules about email addresses as the toparameter to

mail()

The From: Header

The From: header tells the MTA who is sending the email message

If you do not provide a From: header, PHP might or might not add one for you:

n If you are sending email via the sendmail wrapper, PHP will leave it to the MTA

to add a default From: header

n If you are sending email on Windows without using the sendmail wrapper, PHP will use the sendmail_fromsetting in php.inito set a default From: header

Setting the Subject

The second parameter to mail()is a string containing the “subject” of the email

Whatever you put in this string will appear in the Subject: header of the email

Formatting an Email Message

The third parameter to mail()is the email message itself

Plain-Text Emails

Plain-text emails are normal 7-bit US-ASCII strings with each line terminated by \r\n The following code will send a plain-text email, as long as PHP is configured to

correct-ly send email and the MTA is working, too

Note

Some MTAs on UNIX will accept messages that just use \n as the end-of-line sequence This is nonstandard behavior, and you should expect to have problems eventually.