>>I need to tell wether a variable is an array or not. If I do :
>>
>
>Sounds like there is no precise and easy way of knowing if something is an array or not.
>You could try to 'produce' an error :
>
>local llIsNotArray
>on error llIsNotArray = .t.
>alen(laArray)
>on error
>
>if llIsNotArray
>...

What about this one-liner?

IF TYPE("ALEN(laArray)") = "N"  && It's array

TYPE() function does all error handling for you.