PHP Visible Text

<?php
function visibleText($color) {
  $color = trim($color);
  if ($color[0] == '#') {
    $color = substr($color, 1);
    $pound = '#';
  }

  if (strlen($color) == 3) {
    $colors = array(hexdec($color[0] . $color[0]), hexdec($color[1] . $color[1]), hexdec($color[2] .
$color[2]));
  } elseif (strlen($color) == 6) {
    $colors = array(hexdec(substr($color, 0, 2)), hexdec(substr($color, 2, 2)), hexdec(substr($color, 4, 2)));
  } else {
    return $pound . $color;
  }

  if (array_sum($colors) > 255 * 1.5) {
    return $pound . '000';
  } else {
    return $pound . 'FFF';
  };
};