PHP Cookbook

3.7. Finding the Day in a Week, Month, Year, or the Week Number in a Year

Problem

You want to know the day or week of the year, the day of the week, or the day of the month. For example, you want to print a special message every Monday, or on the first of every month.

Solution

Use the appropriate arguments to date( ) or strftime( ):

print strftime("Today is day %d of the month and %j of the year.");
print 'Today is day '.date('d').' of the month and '.date('z').' of the year.';

Discussion

The two functions date( ) and strftime( ) don’t behave identically. Days of the year start with 0 for date( ), but with 1 for strftime( ). Table 3-4 contains all the day and week number format characters date( ) and strftime( ) understand.

Table 3-4. Day and week number format characters

Type	strftime( )	date( )	Description	Range
Day	%d	d	Day of the month, numeric	01-31
Day	%j	z	Day of the year, numeric	001-366 for strftime( ); 0-365 for date( )
Day	%u		Day of the week, numeric (Monday is 1)	1-7
Day	%w	w	Day of the week, numeric (Sunday is 0)	0-6
Day	%W		ISO 8601 day of the week, numeric (Monday is the first day of the week)	0-6
Week	%U		Week number in the year; numeric; first Sunday is the first day of the first week	00-53
Week	%V	W	ISO 8601:1988 week number in the year; numeric; week 1 is the first week that has at least four days in the current year; Monday is the first day of the week	01-53

To print out something only on Mondays, ...