[PHP] Splitting a string by the number of characters in the string?

[Brent Clements]

In PHP 5 there is a awesome function called str_split, is there an equivalent in PHP 
4.x?

I need to do the following:

Split a 60 character string into 3 20 character array chunks.

using str_split I could easily do it, but how do I do it in PHP 4.x?

Thanks,
Brent