(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
   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.
  
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"
?>