PHP filemtime(): Get the Last Modified Time of a File

The PHP filemtime() function is used when we need to find the last time the file was modified. For example:

<?php
   echo "<p>The latest time when the file <b>codescracker.txt</b> was modified:</p>";
   echo filemtime("codescracker.txt");
   echo "<br>Or<br>";
   echo date("d F, Y H:i:s", filemtime("codescracker.txt"));
?>

The output produced by the above PHP example using the filemtime() function is:

Since the filemtime() function returns the last modified time and date of the file in a Unix timestamp, that almost cannot be understood by a normal user. Therefore, let me use the date() function to convert the time into a format that a normal user can understand.

<?php
   $file = "codescracker.txt";
   echo "<p>The file, $file last modified on:</p>";
   
   $mt = filemtime($file);
   if($mt)
   {
      echo "Time: " .date("H:i:s", $mt);
      echo "<br>";
      echo "Date: " .date("d F, Y", $mt);
   }
   else
      echo "Unable to find time, when the file last modified!";
?>

Now the output produced by the above PHP example should be:

PHP filemtime() Syntax

The syntax of the filemtime() function in PHP is:

filemtime(filename)

The function filemtime() returns False on failure.

A frequent application of the filemtime() function is to determine whether a file has been modified since its last access. You can use this function, for instance, to determine if a cache file has expired and must be regenerated.

Advantages of the filemtime() function in PHP

• The ability to retrieve a file's last modified time is its main benefit. This feature can be helpful in a variety of circumstances where you need to know whether a file has been updated since the last time you accessed or processed it.
• Because the entire file does not need to be read into memory, retrieving the file modification time with filemtime() is a comparatively quick operation.
• filemtime() is a built-in PHP function that can access file modification times on a variety of platforms and is supported by the majority of PHP-enabled servers.

Disadvantages of the filemtime() function in PHP

• The filemtime() function only returns the last modified time of a file; it does not return any other details, such as the file's size, owner, or permissions.
• If a file is modified more than once in the same second, filemtime() won't be able to distinguish between those modifications because the resolution of the timestamp it returns is limited to the second.
• If the modification time is not updated when checking for file modifications with filemtime(), the function may return the same timestamp even if the file contents have changed.

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