This appears to be caused by the way my array of arrays is created.

I am creating it in the following manner:

$test[0][0] = 'No';
$test[0][1] = 'Letter';
$test[0][2] = 'Roman';
$test[1][0] = 1;
$test[1][1] = 'a';
$test[1][2] = 'i';
$test[2][0] = 2;
$test[2][1] = 'b';
$test[2][2] = 'ii';
$test[3][0] = 3;
$test[3][1] = 'c';
$test[3][2] = 'iii';
$test[4][0] = 4;
$test[4][1] = 'd';
$test[4][2] = 'iv';
$test[5][0] = 5;
$test[5][1] = 'e';
$test[5][2] = 'v';
$test[6][0] = 6;
$test[6][1] = 'f';
$test[6][2] = 'vi';
[download]

I don't currently see what the difference is from the following (which works):

@test = [
     ['No','Letter','Roman'],
     [1,'a','i'],
     [2,'b','ii'],
     [3,'c','iii'],
     [4,'d','iv'],
     [5,'e','v'],
     [6,'f','vi']
     ];
[download]