Advanced Date/Time Handling with PHP

Welcome!
Advanced Date/Time Handling
ZendCon - Santa Clara, US - Nov 2nd, 2010
Derick Rethans - derick@php.net - twitter: @derickr
http://derickrethans.nl/talks.html
http://joind.in/2232

About Me
Derick Rethans
● Dutchman living in London
● PHP development
● Author of the mcrypt, input_filter, dbus, translit
and date/time extensions
● Author of Xdebug
● Contributor to the Apache Zeta Components
Incubator project (formerly eZ Components)
● Freelancer doing PHP (internals) development

Problems
Timezones
● Most places have whole-hour timezone offsets
● Some places change timezones during the year
● One identifier can mean different zones: PST:
Pacific Standard Time, Pakistan Standard Time
EST: Eastern Standard Time (USA), Eastern
Standard Time (Australia) and Eastern Brazil
Standard Time

Timezone Support
● Bundled timezone database with 564 zones
● Not dependent on timezone abbreviations
● Timezones have the format: Continent/Location or
Continent/Location/Sublocation - Like:
Europe/Amsterdam, America/Indiana/Knox

Changing Timezone Definitions
● An updated database is released about 20 times a
year.
● Some of the changes are very sudden.
● PHP releases will therefore often have an
outdated version.
● The PECL extension timezonedb provides a drop
in replacement for the timezone database.
● pecl install timezonedb

Default Timezones
Setting a default timezone:
<?php
date_default_timezone_set("Europe/Oslo");
$ts = new DateTime("1978-12-22 09:15");
echo $ts->format("e");
?>
Getting a default timezone:
<?php
$default_identifier = date_default_timezone_get();
echo $default_identifier;
?>
Default timezone is 'guessed' in the following order:
● date_default_timezone_set() value
● TZ environment variable
● php.ini's date.timezone setting
● System's rendering of timezone abbreviation

Problems with timestamps and timezones
<?php
$date = strtotime( '2010-03-07 20:48:21 America/Toronto' );
echo date( 'Y-m-d', $date ), "n";
?>
Explanation:
2010-03-07 20:48:21 America/Toronto
1268012901 string is turned into a number
2010-03-08 01:48:21 Europe/London number is
converted to a date/time string using the default
timezone

Parsing Dates
Parsing strings for date time information by
instantiating a DateTime object:
<?php
$dt = new DateTime("2010-03-08 08:43:57");
?>
This function will not return the timestamp as an
integer, but instead returns a DateTime object which
is a wrapper around a 64 bit integer, which you can
access (as string) through:
<?php
$dt = new DateTime("2010-03-08 08:44:12");
echo $dt->format( 'U' ), "n";
?>
The DateTime class is what you can do the really
cool things with.

Parsing Dates
"22apr2006 8:36:14 #^ Europe/Oslo CEST"
"22apr2006 8:36:14 #^ Europe/Oslo CEST"
"22apr2006 8:36:14 Europe/Oslo CEST"
"22apr2006 8:36:14 Europe/Oslo CEST"
Parsing strings with the date_parse() function:
<?php
$date = "22apr2006 8:36:14.43 #^ Europe/Oslo CEST";
$t = date_parse( $date );
echo $t['year'], '-', $t['month'], '-', $t['day'], " ";
echo $t['hour'], ':', $t['minute'], ':', $t['second'] + $t['fraction'], " ";
echo $t['tz_id'], "n";
if ( $t['warning_count'] )
echo "Warnings:n";
foreach( $t['warnings'] as $pos => $message )
echo "- $message @$posn";
if ( $t['error_count'] )
echo "Errors:n";
foreach( $t['errors'] as $pos => $message )
echo "- $message @$posn";

Parsing Dates
08/03/10
08/03/10
August 3rd, 2010
(default)
08/03/10
2008 March 10
08/03/10
8 March 2010

Parsing Dates
With user-defined format
Creating strings with the date_create_from_format()
function:
<?php
$date = "06/08/04";
echo DateTime::createFromFormat( '!d/m/y', $date )->format( DateTime::ISO8601 ), "n";
?>
Parsing strings with the date_parse_from_format()
function:
<?php
$date = "06/08/04";
print_r( date_parse_from_format( '!y*d*m', $date ) );
?>
Example:
Pattern String Y M D
!y*d*m 06/08/04 false false false
!y*d*m 06/08/04 1970 01 01
!y*d*m 06/08/04 2006 01 01
!y*d*m 06/08/04 2006 01 08
!y*d*m 06/08/04 2006 04 08

Modifying Dates
Modifying dates and times:
<?php
date_default_timezone_set("Europe/London");
$ts = new DateTime("2010-03-08 15:53:55");
$ts->modify("+2 days");
$ts->modify("Friday +3 weeks");
$ts->modify("next friday");
?>
Result:
Mon, 08 Mar 2010 15:53:55 +0000
Wed, 10 Mar 2010 15:53:55 +0000
Fri, 02 Apr 2010 15:53:55 +0100
Fri, 09 Apr 2010 15:53:55 +0100

Using Timezones
The Timezone Object
Creating a timezone resource:
<?php
$tz = new DateTimeZone("Asia/Singapore");
?>
Using the timezone when parsing a string with a
date representation:
<?php
$tz = new DateTimeZone("Pacific/Honolulu");
$ts = new DateTime("1978-12-22 09:15", $tz);
?>
A passed timezone object does not override a parsed
timezone:
<?php
$tz = new DateTimeZone("Pacific/Honolulu");
$ts2 = new DateTime("1978-12-22 09:15 Europe/London", $tz);
echo $ts2->format( DateTime::RFC2822 );
?>

Using Timezones
Changing timezones
Using the timezone when parsing a string with a
date representation:
<?php
$tz1 = new DateTimeZone("Pacific/Honolulu");
$tz2 = new DateTimeZone("Australia/Melbourne");
$ts = new DateTime("1978-12-22 09:15", $tz1);
echo $ts->getTimezone()->getName(), ': ',
$ts->format(DateTime::RFC2822), "<br/>";
$ts->setTimezone($tz2);
echo $ts->getTimezone()->getName(), ': ',
$ts->format(DateTime::RFC2822), "<br/>";
?>

Timezones Utilities
Transition Times and Location Information
<?php
$tz = new DateTimeZone("Europe/Berlin");
$trs = $tz->getTransitions(
strtotime('1938-01-01 UTC'), strtotime('1948-01-01 UTC')
);
foreach ($trs as $tr) {
printf("%20s %7d %d %sn",
$tr['time'], $tr['offset'], $tr['isdst'], $tr['abbr']);
}
$loc = $tz->getLocation();
echo 'Info: ', join( ' - ', $loc ), "n";

Timezones Utilities
Restricting listing by geographical location
Restrict by continent:
<?php
$ids = timezone_identifiers_list( DateTimeZone::EUROPE );
echo implode( ", ", $ids );
?>
Restrict by country:
<?php
$ids = timezone_identifiers_list( DateTimeZone::PER_COUNTRY, 'US' );
echo implode( ", ", $ids );
?>

Intervals (PHP 5.3)
Creating an interval
<?php
// full notation
$i = new DateInterval( 'P0003-01-15T06:12:30' );
// abbreviated notation
$i = new DateInterval( 'P3DT6H' );
// from a difference
$d1 = new DateTime();
$d2 = new DateTime( "2010-10-10 10:10 Europe/Amsterdam" );
$i = $d1->diff( $d2 );
// displaying the difference
echo $i->format( '%a days, %h hours, %i minutes' ), "n";
?>
<?php
// create from string
$i = DateInterval::createFromDateString( "next weekday" );
?>

Intervals (PHP 5.3)
Applying an interval
<?php
$d = new DateTime( 'August 27th, 2009' );
echo $d->format( "l Y-m-dn" );
$i = DateInterval::createFromDateString( "next weekday" );
echo $d->add( $i )->format( "l Y-m-dn" );
echo $d->add( $i )->format( "l Y-m-dn" );
$i = DateInterval::createFromDateString( "3 months 10 days" );
echo $d->sub( $i )->format( "l Y-m-dn" );
?>
Result:
Thursday 2009-08-27
Friday 2009-08-28
Monday 2009-08-31
Thursday 2009-05-21

Relative Time
"previous month" / "next month"
<?php
$date = new DateTime( '2010-01-31 15:48:21' );
echo $date->modify( 'next month' )->format( 'Y-m-d' ), "n";
?>
Explanation:
2010-01-31 15:48:21
2010-02-31 15:48:21 "next month" increases month
number by 1
2010-03-03 15:48:21 February only has 28 days, so
days are overflown into the next month

Relative Time
"first day next month"
<?php
echo $date->modify( 'first day next month' )->format( 'Y-m-d' ), "n";
?>
Explanation:
2010-01-31 15:48:21
number by 1
2010-03-03 15:48:21 February only has 28 days, so
days are overflown into the next month
2010-03-04 15:48:21 "first day" adds one more day

Relative Time
"first day *of* next month"
<?php
echo $date->modify( 'first day of next month' )->format( 'Y-m-d' ), "n";
?>
Explanation:
2010-01-31 15:48:21
number by 1
2010-02-01 15:48:21 "first day of" resets the day
number to 1

Relative Time
"last day of third month"
<?php
echo $date->modify( 'last day of third month' )->format( 'Y-m-d' ), "n";
?>
Explanation:
2010-01-31 15:48:21
2010-04-31 15:48:21 "third month" increases month
number by 3
2010-05-00 15:48:21 "last day of" resets the day
number to 0 and increases the month number by 1
2010-04-30 15:48:21 Day count is less than 1, so the
algorithm corrects this to a proper date

Periods (PHP 5.3)
Initializing a period
<?php
// start, interval and count
$db = new DateTime( '2008-07-31' ) ;
$di = DateInterval::createFromDateString( 'next weekday' );
$p = new DatePeriod( $db, $di, 3 );
// start, interval and end
$de = new DateTime ( '2008-08-05' );
$p = new DatePeriod( $db, $di, $de );
// ISO 8601 string
$s = "2008-10-04T20:56:18Z/P0000-00-20T03:15:54/2008-12-22T00:00:00Z";
$p = new DatePeriod( $s );
?>

Periods (PHP 5.3)
Iterating over a period
<?php
$db = new DateTime( '2008-12-31' );
$de = new DateTime( '2009-12-31' );
$di = DateInterval::createFromDateString(
'third tuesday of next month'
);
$dp = new DatePeriod(
$db, $di, $de, DatePeriod::EXCLUDE_START_DATE
);
foreach ( $dp as $dt )
{
echo $dt->format( "F jSn" );
}
?>

php|architect's guide to Date/Time handling

Resources
● This presentation:
● World timezones:
http://www.worldtimezone.com/index24.php
● Geonames: http://www.geonames.org/
● Questions?: derick@php.net

Thanks!
Derick Rethans - derick@php.net - twitter: @derickr
http://joind.in/2232

Advanced Date/Time Handling with PHP

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