array_search in 2-d arrays

I've a 2 D array and would like to search for vals. in the first dimension only i.e. myArray[0][0] myArray[1][0] myArray[2][0] myArray[3][0] . . . and not in the elements myArray[0][1].... CODE: for($l = 0; $l < count($layer); $l++) { $key = array_search($layer[$l], $layerDes); // $layerDes is 2-D $layer[$l] = $layerNames[$key]; } My $key is undefined after execution, is it because the elements are in $layerDes[i][0]? Using $key === also didn't help? Any ideas, thanks. -Pushkar S. Pradhan