Introduction
When you post an article on a blog, you have to display the date that it was published. When you updated a record in a database, you need to record the last update date for auditing purposes. Copyright notices on website need to display the current year too. PHP date functions are the ones that make the above possible. PHP has built in functions that simplify working with date data types.What is the Date Function?
The PHP date function is used to format a date or time into a human readable format. It has the following basic syntax
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| <?phpdate(format,[timestamp]);?> |
- “date(…)” is the function that returns the current time on the server.
- “format” is the general format which we want our output to be i.e.;
- “Y-m-d” for MySQL date format YYYY-MM-DD
- “Y” to display the current year
- “[timestamp]” is optional. If no timestamp has been provided, PHP will get the use the current date and time on the server.
Testing our code
Let’s assume you have saved the file simple_date.php in phptuts, browse to the URL http://localhost/phptuts/simple_date.php
What is a timestamp?
A timestamp is a numeric value in seconds between the current time and value as at 1st January, 1970 00:00:00 Greenwich Mean Time (GMT). The value returned by the time function depends on the default time zone. The default time zone is set in the php.ini file. It can also be set programmatically using date_default_timezone_set function. The code below displays the current time stampAssuming you saved the file timestamp.php in phptuts folder, browse to the URL http://localhost/phptuts/timestamp.php
Getting a list of available time zone identifiers
Before we look at how to set the default time zone programmatically, let’s look at how to get a list of supported time zones.HERE,
- “$timezone_identifiers = DateTimeZone::listIdentifiers();” calls the listIdentifiers static method of the DateTimeZone built in class. The listIdentifiers method returns a list of constants that are assigned to the variable $timezone_identifiers.
- “foreach{…}” iterates through the numeric array and prints the values.
Setting the default time zone programmatically
The date_default_timezone_set function allows you to set the default time zone from a PHP script. The set time zone will then be used by all date function scripts. It has the following syntax.
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| <?phpdate_default_timezone_set ( string $timezone_identifier );?> |
- “date_default_timezone_set()” is the function that sets the default time zone
- “string $timezone_identifier” is the time zone identifier
Assuming you have saved the file set_time_zone.php in the phptuts folder, browse to the URL http://localhost/phptuts/set_time_zone.php
Mktime function
The mktime function returns the timestamp in a UNIX format. It has the following syntax.
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| <?phpmktime(hour, minute, second, month, day, year, is_dst);?> |
- “mktime(…)” is the make timestamp function
- “hour” is optional, it is the number of hour
- “minute” is optional, it is the number of minutes
- “second” is optional, it is the number of seconds
- “month” is optional, it is the number of the month
- “day” is optional, it is the number of the day
- “year” is optional, it is the number of the year
- “is_dst” is optional, it is used to determine the day saving time (DST). 1 is for DST, 0 if it is not and -1 if it is unknown.
HERE,
- “0,0,0” is the hour, minute and seconds respectively.
- “13” is the day of the month
- “10” is the month of the year
- “2012” is the year
PHP Date function reference
The table below shows the common parameters used when working with the date function.Time parameters
| Parameter | Description | Example |
| “r” | Returns the full date and time | |
| “a”,”A” | Returns whether the current time is am or pm, AM or PM respectively | |
| “g”,”G” | Returns the hour without leading zeroes [1 to 12], [0 to 23] respectively | |
| “h”,”H” | Returns the hour with leading zeros [01 to 12],[00 to 23] respectively | |
| “i”,”s” | Returns the minutes/seconds with leading zeroes [00 to 59] |
Day parameters
| Parameter | Description | Example |
| “d” | Returns the day of the month with leading zeroes [01 to 31] | |
| “j” | Returns the day of the month without leading zeroes [1 to 31] | |
| “D” | Returns the first 3 letters of the day name [Sub to Sat] | |
| “l” | Returns day name of the week [Sunday to Saturday] | |
| “w” | Returns day of the week without leading zeroes [0 to 6] Sunday is represent by zero (0) through to Saturday represented by six (6) | |
| “z” | Returns the day of the year without leading spaces [0 through to 365] |
Month Parameters
| Parameter | Description | Example |
| “m” | Returns the month number with leading zeroes [01 to 12] | |
| “n” | Returns the month number without leading zeroes [01 to 12] | |
| “M” | Returns the first 3 letters of the month name [Jan to Dec] | |
| “F” | Returns the month name [January to December] | |
| “t” | Returns the number of days in a month [28 to 31] |
Year Parameters
| Parameter | Description | Example |
| “L” | Returns 1 if it’s a leap year and 0 if it is not a leap year | |
| “Y” | Returns four digit year format | |
| “y” | Returns two (2) digits year format (00 to 99) |
Summary
- The date function is used to format the timestamp into a human desired format.
- The timestamp is the number of seconds between the current time and 1st January, 1970 00:00:00 GMT. It is also known as the UNIX timestamp.
- All date functions use the default time zone set in the php.ini file
- The default time zone can also be set programmatically using PHP scripts.
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