php gives the ability to send arrays from the _GET.
example:
test.php?var1=abc&arr[0]=1&arr[3]=test
will output:
Array
(
[var1] => abc
[arr] => Array
(
[0] => 1
[3] => test
)
)
is this consider bad coding?
No, it’s usual practice. Also it’s natural practice for sending selects with size greater than one.