What are the potential pitfalls of using the lowercase 'w' instead of uppercase 'W' in PHP for calendar week calculation?

Using the lowercase 'w' instead of uppercase 'W' in PHP for calendar week calculation can lead to incorrect week numbers being displayed, as the lowercase 'w' represents the week number starting from Monday, while the uppercase 'W' represents the ISO-8601 week number starting from Sunday. To fix this issue, make sure to use the correct format specifier ('W') when calculating week numbers in PHP. 

$date = new DateTime('2023-12-31');
$weekNumber = $date->format('W');
echo "ISO-8601 week number: " . $weekNumber;

Keywords

php calendar week calculation uppercase

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