Description:
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Add an optional parameter to the shuffle to freeze certain elements in place.

Reproduce code:
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//CURRENTLY
$arrShuffleMe = array(1,2,3,4,5);
shuffle($arrShuffleMe); // produces array(2,4,1,5,3);

//PROPOSED
$arrShuffleMe = array(1,2,3,4,5);
$arrFreezeKeys = array(0,4);
shuffle($arrShuffleMe, $arrFreezeKeys); // produces array(1,3,4,2,5);

$arrShuffleMe = array(1,2,3,4,5);
$arrFreezeKeys = array(0,1);
shuffle($arrShuffleMe, $arrFreezeKeys); // produces array(1,2,4,5,3);

Expected result:
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The shuffle function only shuffles array values whose keys do not match the keys passed in (by array) in the second parameter.

Actual result:
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Feature request. Currently no actual result.