math - PHP round number to 6 decimal places -

i need return result of (1 / n!) * (1! + 2! + 3! + ... + n!), n>=1. codewars challenge! code below returns 1.146652 n = 8, correct result 1.1466510000000001 or 1.146651.

how can truncate number correctly?

function factorial($val){   $factor = 1;   for($i=1;$i<=$val;$i++){     $factor *= $i;   }   return $factor; }  function going($n) {   $val = 1/factorial($n);   $somatorio = 0;   for($i=1;$i<=$n;$i++){     $somatorio += factorial($i);   }    return round($val * $somatorio,6); }