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Basic Zend_Date Operations Common to Many Date Parts

The methods add(), sub(), compare(), get(), and set() operate generically on dates. In each case, the operation is performed on the date held in the instance object. The $date operand is required for all of these methods, except get(), and may be a Zend_Date instance object, a numeric string, or an integer. These methods assume $date is a timestamp, if it is not an object. However, the $part operand controls which logical part of the two dates are operated on, allowing operations on parts of the object's date, such as year or minute, even when $date contains a long form date string, such as, "December 31, 2007 23:59:59". The result of the operation changes the date in the object, except for compare(), and get().

Example 172. Operating on Parts of Dates

<?php
$date 
= new Zend_Date(); // $date's timestamp === time()

// changes $date by adding 12 hours
$date->add('12'Zend_Date::HOUR);
print 
$date;

Convenience methods exist for each combination of the basic operations and several common date parts as shown in the tables below. These convenience methods help us lazy programmers avoid having to type out the date part constants when using the general methods above. Conveniently, they are named by combining a prefix (name of a basic operation) with a suffix (type of date part), such as addYear(). In the list below, all combinations of "Date Parts" and "Basic Operations" exist. For example, the operation "add" exists for each of these date parts, including addDay(), addYear(), etc.

These convenience methods have the same equivalent functionality as the basic operation methods, but expect string and integer $date operands containing only the values representing the type indicated by the suffix of the convenience method. Thus, the names of these methods (e.g. "Year" or "Minute") identify the units of the $date operand, when $date is a string or integer.

List of Date Parts

Table 46. Date Parts

Date Part Explanation
Timestamp UNIX timestamp, expressed in seconds elapsed since January 1st, 1970 00:00:00 GMT.
Year Gregorian calendar year (e.g. 2006)
Month Gregorian calendar month (1-12, localized names supported)
24 hour clock Hours of the day (0-23) denote the hours elapsed, since the start of the day.
minute Minutes of the hour (0-59) denote minutes elapsed, since the start of the hour.
Second Seconds of the minute (0-59) denote the elapsed seconds, since the start of the minute.
millisecond Milliseconds denote thousandths of a second (0-999). Zend_Date supports two additional methods for working with time units smaller than seconds. By default, Zend_Date instances use a precision defaulting to milliseconds, as seen using getFractionalPrecision(). To change the precision use setFractionalPrecision($precision). However, precision is limited practically to microseconds, since Zend_Date uses microtime().
Day Zend_Date::DAY_SHORT is extracted from $date if the $date operand is an instance of Zend_Date or a numeric string. Otherwise, an attempt is made to extract the day according to the conventions documented for these constants: Zend_Date::WEEKDAY_NARROW, Zend_Date::WEEKDAY_NAME, Zend_Date::WEEKDAY_SHORT, Zend_Date::WEEKDAY (Gregorian calendar assumed)
Week Zend_Date::WEEK is extracted from $date if the $date operand is an instance of Zend_Date or a numeric string. Otherwise an exception is raised. (Gregorian calendar assumed)
Date Zend_Date::DAY_MEDIUM is extracted from $date if the $date operand is an instance of Zend_Date. Otherwise, an attempt is made to normalize the $date string into a Zend_Date::DATE_MEDIUM formatted date. The format of Zend_Date::DAY_MEDIUM depends on the object's locale.
Weekday Weekdays are represented numerically as 0 (for Sunday) through 6 (for Saturday). Zend_Date::WEEKDAY_DIGIT is extracted from $date, if the $date operand is an instance of Zend_Date or a numeric string. Otherwise, an attempt is made to extract the day according to the conventions documented for these constants: Zend_Date::WEEKDAY_NARROW, Zend_Date::WEEKDAY_NAME, Zend_Date::WEEKDAY_SHORT, Zend_Date::WEEKDAY (Gregorian calendar assumed)
DayOfYear In Zend_Date, the day of the year represents the number of calendar days elapsed since the start of the year (0-365). As with other units above, fractions are rounded down to the nearest whole number. (Gregorian calendar assumed)
Arpa Arpa dates (i.e. RFC 822 formatted dates) are supported. Output uses either a "GMT" or "Local differential hours+min" format (see section 5 of RFC 822). Before PHP 5.2.2, using the DATE_RFC822 constant with PHP date functions sometimes produces incorrect results. Zend_Date's results are correct. Example: Mon, 31 Dec 06 23:59:59 GMT
Iso Only complete ISO 8601 dates are supported for output. Example: 2009-02-14T00:31:30+01:00

List of Date Operations

The basic operations below can be used instead of the convenience operations for specific date parts, if the appropriate constant is used for the $part parameter.

Table 47. Basic Operations

Basic Operation Explanation
get()

get($part = null, $locale = null)

Use get($part) to retrieve the date $part of this object's date localized to $locale as a formatted string or integer. When using the BCMath extension, numeric strings might be returned instead of integers for large values.

Behaviour of get()

Unlike get(), the other get*() convenience methods only return instances of Zend_Date containing a date representing the selected or computed date or time.

set()

set($date, $part = null, $locale = null)

Sets the $part of the current object to the corresponding value for that part found in the input $date having a locale $locale.

add()

add($date, $part = null, $locale = null)

Adds the $part of $date having a locale $locale to the current object's date.

sub()

sub($date, $part = null, $locale = null)

Subtracts the $part of $date having a locale $locale from the current object's date.

copyPart()

copyPart($part, $locale = null)

Returns a cloned object, with only $part of the object's date copied to the clone, with the clone have its locale arbitrarily set to $locale (if specified).

compare()

compare($date, $part = null, $locale = null)

compares $part of $date to this object's timestamp, returning 0 if they are equal, 1 if this object's part was more recent than $date's part, otherwise -1.


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