[PHP-CLI] Absolute Dirichlet eta function

<?php
function color($value,$range) {
 $value = sqrt($value**2);
 if ($value < $range/6) {
  $r = 255/($range/6)*$value;
  $g = 0;
  $b = 0;
 } elseif ($value >= $range/6 && $value < 2*$range/6) {
  $r = 255;
  $g = 255/($range/6)*($value-$range/6);
  $b = 0;
 } elseif ($value >= 2*$range/6 && $value < 3*$range/6) {
  $r = 255-255/($range/6)*($value-2*$range/6);
  $g = 255;
  $b = 0;
 } elseif ($value >= 3*$range/6 && $value < 4*$range/6) {
  $r = 0;
  $g = 255;
  $b = 255/($range/6)*($value-3*$range/6);
 } elseif ($value >= 4*$range/6 && $value < 5*$range/6) {
  $r = 0;
  $g = 255-255/($range/6)*($value-4*$range/6);
  $b = 255;
 } elseif ($value >= 5*$range/6 && $value < 6*$range/6) {
  $r = 255/($range/6)*($value-5*$range/6);
  $g = 0;
  $b = 255;
 } elseif ($value >= 6*$range/6 && $value < 7*$range/6) {
  $r = 255;
  $g = 255/($range/6)*($value-6*$range/6);
  $b = 255;
 } elseif ($value >= 7*$range/6) {
   $r = 255;
   $g = 255;
   $b = 255;
 }
 return "rgb(" . floor($r) . "," . floor($g) . "," . floor($b) . ")";
}
$str = "";
for ($s = 0; $s <= 3; $s += 0.04) {
    for ($t = 0; $t <= 50; $t += 0.08) {
        $re = 0; $im = 0;
        for ($i = 1; $i <= 1000; $i++) {
            $re -= cos(pi()*$i)*cos($t*log($i))/pow($i,$s);
            $im += cos(pi()*$i)*sin($t*log($i))/pow($i,$s);
        }
        $str .= "<div id='($s,$t)' style='position: absolute; left: ".($t/0.08+2/0.08)."; top: ".($s/0.04+1/0.04).
        "; color: " . color(sqrt(($im)**2+($re)**2),pi())."'>.</div>\n";
    }
    print "$s\n";
}
print $str . "<div style='position: absolute; left: 15px; top: 25px'>..</div>
<div style='position: absolute; left: 15px; top: 50px'>.</div>";
$str2 = "<div style='position: absolute; top: 10px; left: 25px; font-size: 10px'>
|&eta;(s)| = 0 <span style='letter-spacing: -4px'>";
for ($s = 0; $s <= 80; $s++) {
    $str2 .= "<span style='color: " . color($s,70) . "'>&block;</span>";
}
$str2 .= "</span>&nbsp; 7&pi;/6 (that's completely arbitrary)</div>\n";
$fp = fopen("q.html","w");
fwrite($fp,
"<div style='position: absolute; left: 15px; top: 25px'>.</div>
<div style='position: absolute; left: 15px; top: 50px'>.</div>
<div style='position: absolute; left: 15px; top: 75px'>.</div>
<div style='position: absolute; left: 15px; top: 100px'>.</div>\n".$str2.$str);
fclose($fp);
?>