var_export will give you a nice output. Examples from the docs:
$a = array (1, 2, array ("a", "b", "c"));
echo '<pre>' . var_export($a, true) . '</pre>';
Will output:
array (
0 => 1,
1 => 2,
2 =>
array (
0 => 'a',
1 => 'b',
2 => 'c',
),
)