get number of very very small decimal digits

get_number_very_small_decimal_digits.php

<?php
//get_number_very_small_decimal_digits(0.000000000097232321312312);
// return (string) 0.000000000097232321312312

//get_number_very_small_decimal_digits(0.000000098765);
// return (string) 0.000000098765

//get_number_very_small_decimal_digits(0.0000000000987);
// return (string) 0.0000000000987

function get_number_very_small_decimal_digits(float $number, int $decimal = 0): string
{
  if ($number >= 1000)
    return number_format($number, $decimal);
  
  $str = rtrim(number_format($number, 14 - log10($number)), '0');
  $decimal_len = strlen(substr(strrchr($str, "."), 1));
  $format = "%0.".sprintf("%d", $decimal_len)."f";
  return sprintf($format, $number);
}