PHP - Self form submission: $_SERVER['PHP_SELF'] OR action=“”?

[papi_pol]

I just realise that, for some weird circumstances, I was doing what I believe to be self submissions, without any reference to PHP_SELF on the action form attribute.I'm puzzled, can we either use \[code\]<?php echo filter_var($_SERVER['PHP_SELF'], FILTER_SANITIZE_STRING); ?>\[/code\]Or \[code\]action="" \[/code\]?If not, on what circumstances should we considered one, or another?Thanks in advance,MEM