A better php array_merge

I am looking to do this a better way without the need to hardcode the integers for $justPrices[$i]:

$pricesResult = array_merge($justPrices[0], $justPrices[1], $justPrices[2], $justPrices[3]);

$justPrices is a multidimensional array, containing 4 'bands' of prices within each array. The data for $justPrices being for example:

Array ( [0] => Array ( [0] => 40.95 [1] => 39.95 [2] => 39.45 [3] => 38.95 ) [1] => Array ( [0] => 45.80 [1] => 41.80 [2] => 41.50 [3] => 41.40 ) [2] => Array ( [0] => 45.95 [1] => 42.95 [2] => 41.95 [3] => 41.45 ) [3] => Array ( [0] => 50.00 [1] => 50.00 [2] => 50.00 [3] => 50.00 ) )

The issue is that the amount of arrays within $justPrices will vary from at least 2 to 10+. So I need a way for the parameters for the array_merge() function to vary dependent on the amount of arrays within $justPrices. I was going to use this simple method to get the amount of arrays within $justPrices:

$justPricesMax = count($justPrices);

I could write a for loop, and I might still, I just wondered if there was a better method for what seems on the surface relatively simple!