Let's talk about timestamp conversion in php

Timestamp is a way of expressing time in computers and is usually used to record the specific time when an event occurs, such as log records, database records, etc. In PHP, timestamps are also widely used, especially when dealing with time-related businesses, timestamp conversion is particularly important. In this article, we will explore timestamp conversion in PHP and its application in actual development.

1. The concept of timestamp

Unix timestamp, also called POSIX timestamp, refers to the time from 00:00:00 (Greenwich Mean Time) on January 1, 1970 to The total number of seconds now. Since timestamps are measured in seconds, they are highly accurate and can be easily calculated and compared.

In PHP, we can use the time() function to get the current timestamp, for example:

$timestamp = time();
echo $timestamp;

In this way, we can get the current timestamp, and the output result is the value of the current timestamp. , that is, the total number of seconds.

2. Timestamp conversion

1. Time stamp conversion to date time

In actual development, we often need to convert timestamps into specific Date and time, we can use the date() function to achieve this, for example:

$timestamp = time();
$date_time = date('Y-m-d H:i:s', $timestamp);
echo $date_time;

In this way, the current timestamp can be converted into a string of date and time, and the output result will be similar to "2021-01 -01 12:00:00" format.

In the date() function, the first parameter is the format string. You can customize the format according to your needs. Commonly used formatting characters include:

Y：表示年份，例如“2021”；
m：表示月份，例如“01”；
d：表示日期，例如“01”；
H：表示小时，例如“12”；
i：表示分钟，例如“00”；
s：表示秒钟，例如“00”；

More formatting characters You can refer to PHP official documentation.

2. Date time to timestamp

Similarly, if we have a date and time string, we can also convert it to a timestamp, for example:

$date_time = '2021-01-01 12:00:00';
$timestamp = strtotime($date_time);
echo $timestamp;

In this way, the date and time string "2021-01-01 12:00:00" can be converted into a timestamp, and the output result is the total number of seconds.

In the strtotime() function, we can pass in a date and time string as a parameter, and the function will parse it into a timestamp and return the result.

3. Application examples

Time stamp conversion is widely used in actual development. Below we use a simple example to illustrate its application.

Suppose we have a user table that contains a last_login_time field, which is used to record the time when the user last logged in. In order to facilitate recording and query, we want to store it in the form of date and time.

Then we can get the current timestamp through the time() function after the user successfully logs in, then call the date() function to convert it into a date and time string, and finally update it to the database.

$timestamp = time();
$date_time = date('Y-m-d H:i:s', $timestamp);

// 更新用户表
$update_sql = "UPDATE user SET last_login_time = '$date_time' WHERE id = $user_id";

When we need to query the last login time of the user in the future, we only need to read the corresponding value from the database, then call the strtotime() function to convert it into a timestamp, and finally call date() The function converts the timestamp into a datetime string.

// 从数据库中读取last_login_time字段
$select_sql = "SELECT last_login_time FROM user WHERE id = $user_id";
$result = mysqli_query($conn, $select_sql);
$row = mysqli_fetch_assoc($result);
$last_login_time = $row['last_login_time'];

// 将日期时间字符串转换为时间戳
$timestamp = strtotime($last_login_time);

// 将时间戳转换为日期时间字符串
$date_time = date('Y-m-d H:i:s', $timestamp);

echo "你最后一次登录的时间是：" . $date_time;

Through the above examples, we can see the application of timestamp conversion in actual development, which can easily realize the storage and reading of date and time.

4. Summary

This article mainly introduces the concept and conversion method of timestamp in PHP, including two methods of converting timestamp to date and time and converting date and time to timestamp. It also gives A practical application example, I hope it can be helpful to everyone in actual development.

When using timestamp conversion, you need to pay attention to the time zone issue. Because the timestamp is based on Greenwich Time, you need to consider the impact of the time zone when converting, otherwise time inconsistencies may occur. .

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