date weekday php code example
Example: php week of a date
Things to be aware of when using week numbers with years.
<?php
echo date("YW", strtotime("2011-01-07"));
echo date("YW", strtotime("2011-12-31"));
echo date("YW", strtotime("2011-01-01"));
?>
BUT
<?php
echo date("oW", strtotime("2011-01-07"));
echo date("oW", strtotime("2011-12-31"));
echo date("oW", strtotime("2011-01-01"));
?>
Reason:
Y is year from the date
o is ISO-8601 year number
W is ISO-8601 week number of year
Conclusion:
if using 'W' for the week number use 'o' for the year.