How can I "dual" implode a nested array?

Question

I have a nested array (only one level deep) like this:

$a = array(
  array( 1, 2, 3 ),
  array( 2, 4, 6 ),
  array( 5, 10, 15 )
  );

And I'd like a nice way to implode() it to this form:

1,2,3|2,4,6|5,10,15

I can run a loop to implode(',',...) each array in $a (storing those strings in a temp), and then implode('|',...) that temporary array, but it seems like I should be able to do this more concisely* with PHP.

Thanks in advance,
Cheers!

*By "more concisely" I mean, without writing a loop (so, just using function calls)

Answer 1

Here is a really dirty way:

str_replace('],[', '|', trim(json_encode($a), '[]'));

Answer 2

I'm late to the game here (by SO standards) but you could literally "dual" implode.

implode('|', array_map('implode', array_fill(0, count($a), ','), $a))