Please tell me the description of smarty that branches conditions according to the flag set in the URL.

Thank you for your help.I'm afraid it's rudimentary, but please give me some advice.

The description of conditional branching according to the flag in the URL is as follows in PHP, but could you tell me what the description would be like if a similar case was described in smarty?

if($_GET['id']=='1'){
a;
} else if($_GET['id']=='2'){
b;
} else if($_GET['id']=='3'){
c;