PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

476 Chapter 21 Managing the Date and Time
It is important to note that whenever it says standard format in Table 21.3, the formatting
code gets replaced by the associated value according to the web server’s local settings.
The strftime() function is very useful for displaying dates and times in a variety of different
ways to make your pages more user friendly.
Converting Between PHP and MySQL Date
Formats
Dates and times in MySQL are handled in ISO 8601 format.Times work relatively intuitively,
but ISO 8601 requires you to enter dates with the year first. For example, you
could enter March 29, 2008, either as 2008-03-29 or as 08-03-29. Dates retrieved from
MySQL are also in this format by default.
Depending on your intended audience, you might not find this function very user
friendly.To communicate between PHP and MySQL, then, you usually need to perform
some date conversion.This operation can be performed at either end.
When putting dates into MySQL from PHP, you can easily put them into the correct
format by using the date() function, as shown previously. One minor caution if you are
creating them from your own code is that you should store the day and month with
leading zeros to avoid confusing MySQL.You can use a two-digit year, but using a fourdigit
year is usually a good idea. If you want to convert dates or times in MySQL, two
useful functions are DATE_FORMAT() and UNIX_TIMESTAMP().
The DATE_FORMAT() function works similarly to the PHP function but uses different
formatting codes.The most common thing you want to do is format a date in normal
American format (MM-DD-YYYY) rather than in the ISO format (YYYY-MM-DD)
native to MySQL.You can do this by writing your query as follows:
SELECT DATE_FORMAT(date_column, ‘%m %d %Y’)
FROM tablename;
The format code %m represents the month as a two-digit number; %d, the day as a twodigit
number; and %Y, the year as a four-digit number. A summary of the more useful
MySQL format codes for this purpose is shown in Table 21.4.
Table 21.4
Code
Format Codes for MySQL’s DATE_FORMAT() Function
Description
%M Month, full text
%W Weekday name, full text
%D Day of month, numeric, with text suffix (for example, 1st)
%Y Year, numeric, four digits
%y Year, numeric, two digits
%a Weekday name, three characters
%d Day of month, numeric, leading zeros