PHP fade/mute zeroes in decimals

format_btc.php

<?php
function formatBtc($val){
  $val = number_format($val, 8); // round to 8 decimal points
  $rtval = rtrim($val, "0"); // get rid of zeroes at the end
  $x = strlen($val) - strlen($rtval); // get how many zeroes were deleted
  if($x > 0){
    $rtval .= '<span style="color:#ffffff6f;">'; // start a "faded" <span>
    // or try class="text-muted" for bootstrap
    for($i = 0;$i < $x;$i++) // add deleted zeroes back
      $rtval .= "0";
    $rtval .= "</span>";
  }
  return $rtval;
}