Timestamp handling in PHP: How to convert datetime to timestamp using strtotime function

Timestamp processing in PHP: How to use the strtotime function to convert a date time into a timestamp

The timestamp refers to the seconds from January 1, 1970 00:00:00 (Greenwich Mean Time) to the present number. In PHP, we often need to convert between dates and times, making it easier for us to perform time operations. PHP provides the strtotime function to convert date time into a timestamp. Let's take a look at how to use the strtotime function correctly.

First, let's look at a simple example. Suppose we have a datetime string "2021-01-01 12:00:00" and we want to convert it to a timestamp. You can use the following code:

$date_string = "2021-01-01 12:00:00";
$timestamp = strtotime($date_string);

echo "时间戳：".$timestamp;

The output result will be the timestamp corresponding to the date and time.

When using the strtotime function, we can pass date and time strings in various formats, and it will automatically recognize and convert them into timestamps. The following are some commonly used date and time string formats and their corresponding conversion results:

1. "2020-01-01": will be converted to a timestamp of 00:00:00AM on this date.
2. "2020-01-01 12:00:00": will be converted to a timestamp of this date and time.
3. "January 1, 2020": Will be converted to a timestamp of 00:00:00AM Beijing time.
4. "2020-01-01 12:00pm": will be converted into a timestamp of this date and time. Note that the time is in 12-hour format.
5. "2020-01-01 12:00:00 0800": Will be converted to a timestamp of this date and time. Note that the time zone is specified as 0800 (Beijing time).

In addition to date and time strings, the strtotime function can also handle some relative strings, such as:

1. "1 day ago": represents the timestamp 1 day ago .
2. "next week": Indicates the timestamp of next week.
3. "last day of month": Indicates the timestamp of the last day of this month.
4. " 2 weeks": Indicates the timestamp 2 weeks later.

When the strtotime function processes these relative strings, it will automatically calculate the correct timestamp based on the current time.

It should be noted that the strtotime function can only handle dates and times after 1970. If you pass a date and time before 1970, false will be returned. In addition, the strtotime function will also give a default time for incomplete date and time strings (for example, only year and month), which is generally 00:00:00AM.

In project development, processing timestamps is a very common operation. We can use the strtotime function to convert a datetime string into a timestamp, and then use the timestamp to perform various time operations, such as comparisons, calculations, etc.

To summarize, you can easily convert a datetime string to a timestamp using the strtotime function. Whether it is processing date and time strings in a specific format, or processing relative time strings, the strtotime function can accurately give the corresponding timestamp. In project development, rational use of the strtotime function can make it easier for us to handle time-related tasks.

Reference materials:

• [PHP official document - strtotime function](https://www.php.net/manual/en/function.strtotime.php)

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