(PHP 5 >= 5.5.0, PHP 7)
Add/insert a new value at the specified index
public void SplDoublyLinkedList::add ( mixed $index, mixed $newval )
Insert the value newval at the specified index, shuffling the previous value at that index (and all subsequent values) up through the list.
Parameters:
index
The index where the new value is to be inserted.
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