$filePath = dirname(__FILE__) . '/test.txt'; $absFilePath = realpath($filePath); echo $absFilePath;In this example, we are first defining the file path relative to the current file using the "__FILE__" constant. Then we are using the "realpath()" function to get the absolute path of this file. Finally, we are echoing out the result. Package library: The package library used in this example is the PHP Standard Library. This library contains a variety of built-in functions and constants that can be used in PHP applications. The "realpath()" function, which is used in this example, is included in this library.