Use PHP filemtime() function to get file modification date

In website development, we often need to obtain the last modification date of a file, such as the modification date of an article in a blog, the update time of the website, etc. In PHP, we can use the filemtime() function to obtain the last modification time of the file to achieve such a function. This article will introduce in detail how to use the PHP filemtime() function to get the last modification time of a file.

1. What is the filemtime() function

In PHP, the filemtime() function is a function used to obtain the last modification time of a file. Its syntax is as follows:

int filemtime(string $filename)

Among them, $filename represents the path and file name of the file, and the function will return the UNIX timestamp of the last modification time of the file. If the file does not exist or cannot be read, the function returns false.

2. How to use the filemtime() function

Getting the last modification time of a file can help us implement some very useful functions. For example, we can determine whether a file has expired based on the last modification time, or display the update time of a file based on the last modification time. The following is an example code that uses the filemtime() function to get the last modification time of a file:

$file = 'example.txt';
if (file_exists($file) ) {

echo '文件的最后修改时间是：'.date("Y-m-d H:i:s", filemtime($file));

} else {

echo '文件不存在';

}
?>

In this example, we first use the file_exists() function to check whether the file exists, If the file exists, the last modification time of the file is output, otherwise "the file does not exist" is output. When outputting the last modification time, we use the date() function to convert the UNIX timestamp into a common date and time format. The output content may be similar to the following:

The last modification time of the file is: 2021-07-08 14:30:24

If we modify the example.txt file and run this again Code, the last modification time of the output will be updated to the latest modification time.

3. Other Notes

In addition to using the filemtime() function, we can also use some other functions to obtain the attribute information of the file. For example, we can use the filesize() function to get the size of the file, use the fileperms() function to get the permission information of the file, and so on. These functions can help us manipulate file attribute information more conveniently.

In addition, some operating systems do not support the last modification time of files or the time precision of the file system is relatively low, which may cause the timestamp returned by the filemtime() function to be inaccurate. During the development process, we should fully understand the characteristics of the operating system and file system, and use these functions reasonably to obtain file attribute information.

4. Summary

This article introduces how to use the PHP filemtime() function to get the last modification time of a file. This function can help us implement functions such as blog post modification date and website update time. When using this function, we need to pay attention to the existence of the file and the characteristics of the operating system and file system to ensure the correctness and reliability of the program. Finally, I hope this article can be helpful to PHP developers.

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