your regex is being greedy. you need to stop it being greedy to do what you want. Find out a bit more about greediness here.
When a match is greedy it will ignore the first situation which satisfies the regex and will keep trying to match until it consumes as much of the input as it can.
Usually this involves adding a ?
but I'm not certain in php, but you could try:
preg_match_all("^[(.*?)]^",$html,$fields, PREG_PATTERN_ORDER);
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