Detailed explanation of how php strtotime() and date() functions handle timestamps

In PHP, to convert date time and timestamp into each other, you can use the built-in functions strtotime() and date(). A timestamp is a number that represents time, representing the number of seconds since January 1, 1970 00:00:00 UTC.

Here are the detailed steps on how to use strtotime() and date() functions to process timestamps.

1. Use the strtotime() function to convert a date and time string into a timestamp

The strtotime() function can convert a date and time that conforms to a certain format Convert string to timestamp. The syntax is as follows:

$timestamp = strtotime($date_time_string);

Among them, $date_time_string represents the date and time string to be converted, which can be a specific date and time, or it can be in a format relative to the current time, for example, "-1 day" represents yesterday, "1 week ago" means one week ago.

The following code demonstrates how to convert a specific date and time string into a timestamp:

$date_time_string = '2022-01-01 12:00:00';
$timestamp = strtotime($date_time_string);
echo $timestamp;  // 输出：1641043200

2. Use the date() function to format the timestamp into a date and time String

#date() function can format the timestamp into a date and time string that conforms to a certain format. The syntax is as follows:

$date_time_string = date($format, $timestamp);

Among them, $format represents the format of the date and time string, and $timestamp is the timestamp to be converted.

The following code demonstrates how to format a timestamp into a regular date and time string:

$timestamp = 1641043200;
$date_time_string = date('Y-m-d H:i:s', $timestamp);
echo $date_time_string;  // 输出：2022-01-01 12:00:00

Through the above two steps, we can easily convert date and time into a timestamp , and convert the timestamp into a date and time string. In practical applications, timestamps are often used for comparison and calculation of dates and times. For example, we can determine the order by comparing the sizes of two timestamps, or we can calculate the time interval by adding and subtracting timestamps.

If you are using PHP 5.3.0 and above, you can also use the DateTime class and related methods for date and time conversion and calculation. Using the DateTime class can make your code more readable and flexible.

The above is the basic operation of converting PHP into timestamp. I hope it will be helpful to you.

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