PHP Filesystem fileowner() Function

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The PHP Filesystem fileowner() function is used to return the user ID (owner) of the given file. This function can return the User ID on success or false on failure.

The result of this function can be cached, so we can use clearstatcache() function to clear the cache. This function can not be run on Windows systems. We can use the posix_getpwuid() function to convert User ID to the username.

Syntax

Below is the syntax of the PHP Filesystem fileowner() function −

int fileowner ( string $filename )

Parameters

The parameters are needed to use the fileowner() function are mentioned below −

Return Value

It returns the user ID (UID) of the owner of the file on success and if the function fails it returns FALSE.

PHP Version

The fileowner() function was first introduced as part of core PHP 4 and work well with the PHP 5, PHP 7, PHP 8.

Example

This is the basic example of showing the usage of the PHP Filesystem fileowner() function in which we are trying to get the owner of the file provided in the path.

<?php
   // echo the Owner ID of the file 
   echo fileowner("/PhpProject/sample.txt");
?>

Output

This will produce the following result −

0

Example

In the below PHP code we will use fileowner() function and also handle the error in case if we will not be able to get the file ID or if the file is not present.

<?php
   // Provide file path here
   $filename = "/PhpProject/myfile.txt";
   
   // use fileowner() function to get file ID
   $owner = fileowner($filename);

   // Handle the error here
   if ($owner !== false) {
      echo "The owner of the file is: " . $owner;
   } else {
      echo "Failed to get the owner of the file.";
   }
?> 

Output

This will generate the below result −

The owner of the file is: 501

Example

The fileowner() function is used to get the owner of the given directory in our case it is 'uploads/'' directory. The code checks if the function returns a valid user ID.

<?php
   $uploadDir = "uploads/";
   $owner = fileowner($uploadDir);

   if ($owner !== false) {
      echo "The owner of the upload directory is: " . $owner;
   } else {
      echo "Failed to get the owner of the upload directory.";
   }
?> 

Output

This will create the below outcome −

The owner of the upload directory is: 302

Example

The below example performs checking the owner of a log file error_log using the fileowner() function and return the value of it as owner ID.

<?php
   // define the log file here
   $logFile = "error_log";

   // get the owner id of the file
   $owner = fileowner($logFile);

   // perform error handling
   if ($owner !== false) {
      echo "The owner of the log file is: " . $owner;
   } else {
      echo "Failed to get the owner of the log file.";
   }
?> 

Output

This will lead to the following outcome −

The owner of the log file is: 1001

Note

You should verify to make sure the script has the right permissions to access the file and that it actually exists. When file ownership is required for logging, file management, or security checks, this function is really useful.

Summary

The user ID (UID) of the file or directory owner can be obtained using a built-in PHP function called fileowner(). It takes only the file path as an argument, and returns false if it cannot find the UID. This feature is present in all versions of PHP and is required for tasks that need file owner verification.