php.ini contains your PHP config settings. if you are moving across different PHP major and point revisions, its possible that each version has its own php.ini file in its directory. such as php 7.2 and 7.3 are normally kept separate.
https://www.php.net/manual/en/configuration.file.phpmany hosts may have another config file that takes your php settings and passes them to other php point revision updates. you may also be passing php settings along through an .htaccess file in an upper level directory.
all of this is beyond the scope of conversation for this release of UBB.threads. google is your friend for further research, asking your host is also good advice
