Getting the number of weeks corresponding to dates in PHP can be achieved through built-in functions. The main methods are: 1. Use the date() function to match the 'W' formatter to obtain the ISO-8601 standard number of weeks, such as $weekNumber = date('W', strtotime('2025-04-05')); 2. Use the DateTime class to process time and time zones more flexibly, such as $date = new DateTime('2025-04-05'), $weekNumber = $date->format('W'); 3. Custom logic adapts to the differences in weekly start days in different regions. If the weekly start date is set to Sunday, the date calculation needs to be manually adjusted. Note that the return value is a string, the judgment rules for the first week and the cross-time zone processing issues. It is recommended to choose the appropriate method according to business needs.

It is actually quite straightforward to get the number of weeks corresponding to the date in PHP, and it can be done with built-in functions. The key is to understand the differences in weekly starting days in different regions. For example, some places start Monday as Monday, while others start on Sunday. PHP is calculated by default according to ISO-8601, that is, Monday is the first day of the week, and the first week must include at least four days.

Use the date function to get the number of weeks

The easiest way is to use date() function to match the format 'W' :

 $date = '2025-04-05';
$weekNumber = date('W', strtotime($date));
echo "Week number: $weekNumber";

This code will output the number of weeks for the corresponding date, such as Week number: 14 . Note that the returned string is a string, and if integers are needed, you can cast it.

• If the date you passed in is 2025-01-01 , it may belong to the last week of the previous year, 53 the number of weeks returned at this time may be 00 or 52 .
• This method is processed according to the local time zone by default. If you are dealing with time across time zones, it is recommended to use the DateTime class to clearly set the time zone.

Use the DateTime class to control more flexibly

If you want to control the time, time zone more accurately or do further operations, it is recommended to use DateTime class:

 $date = new DateTime('2025-04-05');
$weekNumber = $date->format('W');
echo "Week number: $weekNumber";

This method is the same as the above results, but the advantage is that it can be chained calls, modifying time, setting time zones, etc. For example:

 $date = new DateTime('2025-01-01', new DateTimeZone('Europe/London'));
$weekNumber = $date->format('W');

This way you don't have to worry about problems caused by the server's default time zone.

Pay attention to regional differences: Different weekly start dates will affect the results

Different countries and regions have different habits about "when day the week starts":

• Most European, ISO standards: Monday
• Most parts of the United States and Canada: Sunday

If you want to calculate the number of weeks based on local habits, you can't just rely on 'W' , you have to write your own logical judgment.

For example, you want the week to start on Sunday:

 $date = '2025-04-05';
$timestamp = strtotime($date);
$dayOfWeek = date('w', $timestamp); // 0=Sunday, 1=Monday...
$offset = ($dayOfWeek 6) % 7; // Calculate how many days there are from the most recent Monday $adjustedDate = $timestamp - ($offset * 86400); // Adjust to the Monday of the week $weekNumber = floor((strtotime(date('Ym-d', $adjustedDate)) - strtotime(date('Y', $adjustedDate) . '-01-01')) / 604800) 1;
echo "Week number (starting from Sunday): $weekNumber";

Although this method is complex, it can adapt to the non-ISO weekly starting method.

Basically that's it. It is not difficult to obtain the number of weeks with PHP, but you need to choose the right method according to the business scenario, especially when it comes to multilingual and multi-regional areas, don’t forget to consider the definition differences between the starting day of the week and the first week.

The above is the detailed content of php get week number from date. For more information, please follow other related articles on the PHP Chinese website!