(PHP 5 >= 5.3.0, PHP 7, PHP 8, PECL phar >= 2.0.0)
Phar::running — Returns the full path on disk or full phar URL to the currently executing Phar archive
$returnPhar = true): string
   Returns the full path to the running phar archive.  This is intended for use much
   like the __FILE__ magic constant, and only has effect inside
   an executing phar archive.
  
   Inside the stub of an archive, Phar::running() returns
   "".  Simply use __FILE__
   to access the current running phar inside a stub.
  
returnPhar
       If false, the full path on disk to the phar
       archive is returned.  If true, a full phar URL is returned.
      
Returns the filename if valid, empty string otherwise.
Example #1 A Phar::running() example
     For the following example, assume the phar archive is located
     at /path/to/phar/my.phar.
    
<?php
$a = Phar::running(); // $a is "phar:///path/to/my.phar"
$b = Phar::running(false); // $b is "/path/to/my.phar"
?>