if someone can help me, to install mcrypt and modify php
I guess you have a major problem. Php 7.2 isn't supported yet.
Also, I guess mcrypt is enabled by default with Xampp. Am I right?
Here is the solution **mcrypt error** for PHP 7.2 + versions In Xampp, wamp, etc
Just follow the below link and download ext in the "Dell List" section. like 7.4 Thread Safe (TS) x64
Unzip file and paste both (php_mcrypt.pdb, php_mcrypt.dll) files in PHP>ext folder. Next Edit the php.ini file and add the extension
below "; Dynamic Extensions". Restart apache, it's work for me.
Found something useful, "Kudos" and "Accept as Solution" for Token of Appreciation
As others have stated you cannot install mcrypt in xampp because
Php 7.2 is not yet supported. You can also check the PHP manual,
which states that this feature was removed in PHP 7.2.0. So, it only
works on a lower version.