How php variable names change with parameters-php Tutorial

I have not written php variable names that change with parameters. I would like to know how php variable names change with parameters.
For ($ I = 1; $ I <= 3; $ I ++ ){
$ ItemId $ I = $ I;
}
?>

The output result is
$ ItemId1 = 1;
$ ItemId2 = 2;
$ ItemId3 = 3;

How can I fill in the for loop above. Thank you.

Reply to discussion (solution)

For ($ I = 1; $ I <= 3; $ I ++) {$ {"itemId $ I" }=$ I;} echo $ itemId1; // 1 echo $ itemId2; // 2 echo $ itemId3; // 3

Thank you very much. I have never written php and do not know the rules. Solved