Spelling can still be phonetic even if groups of letters have differing sounds from those letters' sounds serially in isolation. The key criterion is that the rules must be universal, applying to every instance of those groupings, rather than having exceptions for their appearances in certain words.
...ok, it occurs to me now that a smart-alec might declare each individual word to be a "grouping of letters with its own phonetic pronounciation", whereupon phoneticism as-defined is achieved trivially because pronounciation is universal over the singleton universe of words spelt exactly like that word. You know what I _mean_ - "sufficiently small groups of letters", hand-wave.
