That´s quite a workaroud. Liked it. Very creative.

Test4 and last test print the same but these two cases are different. To avoid errors I will suppress my printing so that you can print and see yourself.
Re-read carefully the description (think of possible edge cases, see the remarks). Be sure that there are no errors in the tests. Cheers.

I totally re-wrote the C++ translation. Maybe you could have a look.

The pown function can cause an overflow exception, e.g:

pown Int64.MaxValue 2 // => OverflowException

Int64.MaxValue * Int64.MaxValue // => 1

$a1 = [121, 144, 19, 161, 19, 144, 19, 11];
$a2 = [11*11, 121*121, 144*144, 19*19, 161*161, 19*19, 144*144, 19*19];
$this->revTest(comp($a1, $a2), true);

Maybe you don't read correctly the result of the test: the expected result is true and you returned false.

PS: See the top of the page, 576 guys passed the PHP kata. If there were errors one can hope that somebody would have already seen them!

Found bug in PHP testcase

  $a1=array (  0 => 121,  1 => 144,  2 => 19,  3 => 161,  4 => 19,  5 => 144,  6 => 19,  7 => 11,);
  $a2=array (  0 => 121,  1 => 14641,  2 => 20736,  3 => 361,  4 => 25921,  5 => 361,  6 => 20736,  7 => 361,);
  $this->revTest(comp($a1, $a2), true);

It is true, but in Attemt's testBasics it is expected false - http://prntscr.com/lxt4ma .

Please, check expected result in this test in Attempt's testBasics.