Added diff and intersect to the Hash object making the primes example even smaller.

  /*python version*/
  noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]
  primes = [x for x in range(2, 50) if x not in noprimes]

  /*common php version*/
  $noprimes = xR(2,8)->mapf('xR($x*2,50,$x)->out()')->flatten();
  $primes = xR(2,50)->diff($noprimes);

Or as a lovely one liner

  $primes = xR(2,50)->diff(xR(2,8)->mapf('xR($x*2,50,$x)->out()')->flatten());

A little less readable for sure but the reality is it can be done and it fits the true definition of "one liner" by sliding in at the 79th column.