How to Retrieve a File’s Last Modification Time in PHP

Getting a file’s last modification time is useful for tracking updates or determining when a file needs to be reloaded. In PHP there are several ways to obtain this timestamp.

Using filemtime() function

The filemtime() function is the simplest method; it returns the Unix timestamp of the given file since January 1, 1970.

$timestamp = filemtime('file.txt');

Using stat() function

The stat() function returns an array containing information about the file, including the modification time.

$result = stat('file.txt');
$timestamp = $result['mtime'];

Using DateTime object

You can use the DateTime object to obtain the file’s last modification time; the object can parse timestamps.

$timestamp = filemtime('file.txt');
$date = new DateTime();
$date->setTimestamp($timestamp);
echo $date->format('Y-m-d H:i:s');

Practical example

Assume you have a file named file.txt and you want to notify the user when the file has changed since it was last read.

The following demonstrates using filemtime() to achieve this:

$last_modified = filemtime('file.txt');

if ($last_modified > $_SESSION['last_read']) {
    // File has been modified
    echo 'File has been updated!';
    $_SESSION['last_read'] = $last_modified;
}

Java learning material

C language learning material

Frontend learning material

C++ learning material

PHP learning material