in reply to Untillian Headache or about the semantic of until
The first thing I noticed is that the ordering of the sub conditions is probably wrong in the original.
As constructed, if $wheel < 0, it won't be detected until after the first sub condition has already accessed a negative subscripted array element, which is almost certainly wrong.
So, I'd suggest you start with switching that around: until( $wheel < 0 || $odometer[ $wheel ] > 9 ) { ....
Then, I'd suggest you translate that into prose in your preferred language. (I use English; for you probably Italian?).
Loop, until the array index reduces past the start of the array; or, the value of the array element at the current index is greater than 9.
Then invert the logic of that prose description:
Loop, while the array index hasn't reduced past the start of the array; and, the value of the array element at the current index is less than or equal to 9.
And then translate it back to code: while( $wheel >=0 && $odometer[ $wheel ] <=9 ) {
And finally, the inevitable question about why you want to do that anyway?
How do Italian recipes phrase the common situation: Bake for 15 minutes or until the cheese is melted and bubbling.