Removing php array duplicates with regard to a few specific indexes
Suppose I have a multi-dimensional array with 100's of sub-arrays.  The sub-arrays always have at least 3 indexes, but can have more.  I'd like to remove from the big array all the sub-arrays which are duplicates of others *in regards to those three indexes*.  Example with an array that only has two sub-arrays:

    array(array(0 => 'a', 1=> 'b', 2 => 'c', 3 => 'd'), array(0 => 'a', 1=> 'b', 2=> 'c', 3=> 'z'))

one of the sub-arrays would be removed, because the first 3 indexes match even though the 4th does not.

I'm looking for the most elegant/efficient solution.
Removing php array duplicates with regard to a few specific indexes
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Suppose I have a multi-dimensional array with 100's of sub-arrays.  The sub-arrays always have at least 3 indexes, but can have more.  I'd like to remove from the big array all the sub-arrays which are duplicates of others *in regards to those three indexes*.  Example with an array that only has two sub-arrays:

    array(array(0 => 'a', 1=> 'b', 2 => 'c', 3 => 'd'), array(0 => 'a', 1=> 'b', 2=> 'c', 3=> 'z'))

one of the sub-arrays would be removed, because the first 3 indexes match even though the 4th does not.

I'm looking for the most elegant/efficient solution.