Description:
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Currently XSLTProcessor does not accept any parameters for constructor.

However it has to be used with a stylesheet, so why not accept it in constructor?

That'd make typical usage simpler/shorter.

It will be 100% backwards-compatible if parameter is optional.

Expected result:
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$proc = new XSLTProcessor($sheet);

Actual result:
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$proc = XSLTProcessor();
$proc->importStylesheet($sheet);