About PHP regular matching. Ask for advice

About PHP regular matching problem ... For advice
[Q] Thank you for your selfless help. () [A] Thank you [B] Thank you very much [C] Thank you very much [D] Thank you [E] ten Thank you [F] hundred Thank you [k]d

For the above-mentioned string how to use the regular will [Q], [A], [B], [C], [D], [E], [F], [K] out, the remaining string combination of the group, ask you big!
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$s = ' $Q] Thank you so much for your selfless help. (     ) [A] Thank you [B] Thank you very much [C] Thank you very much [D] Thank you [E] ten Thank you [F] hundred extremely grateful [k]d ';
$ar = Preg_split ('/\[[a-z]\]/', $s);

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