The function below will show the sunrise or sunset time of the day $yday for a place based on its latitude and longitude information.

It works well with php3.x and php4.x until 4.0.1pl2, but in php4.0.2, it will give the same result for all sunrise and sunset and whatever latitude and longitude information passed to it. Some calculating function might not function well in the version of php...

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  function suntime ($latitude, $longitude, $timezone, $yday) {
    $A = 1.5708;
    $B = 3.14159;
    $C = 4.71239;
    $D = 6.28319;
    $E = 0.0174533 * $latitude;
    $F = 0.0174533 * $longitude;
    $G = 0.261799  * $timezone;
    $R = -.0145439;

    for ($i = 0; $i < 2; $i++)
    {
      if (!$i) {$J =  $A;  $type = "rise";}
        else  {$J =  $C;  $type = "set"; }
      $K = $yday + (($J - $F) / $D);
      $L = ($K * .017202) - .0574039;           // Solar Mean Anomoly
      $M = $L + .0334405 * sin($L);             // Solar True Longitude
      $M += 4.93289 + (3.49066E-04) * sin(2 * $L);

      // Quadrant Determination
      if ($D == 0) {exit;}
      while ($M < 0)   {$M = ($M + $D);}
      while ($M >= $D) {$M = ($M - $D);}

      if (($M / $A) - intval($M / $A) == 0) {$M += 4.84814E-06;}
      $P = sin($M) / cos($M);                   // Solar Right Ascension
      $P = atan2(.91746 * $P, 1);

      // Quadrant Adjustment
      if ($M > $C) {$P += $D;}
      else {if ($M > $A) {$P += $B;} }

      $Q = .39782 * sin($M);              // Solar Declination
      $Q = $Q / sqrt(-$Q * $Q + 1);
      $Q = atan2($Q, 1);
      $S = $R - (sin($Q) * sin($E));
      $S = $S / (cos($Q) * cos($E));

      if (abs($S) > 1) {echo 'none';}     // Null phenomenon

      $S = $S / sqrt(-$S * $S + 1);
      $S = $A - atan2($S, 1);

      if ($type == 'rise') {$S = $D - $S ;}

      $T = $S + $P - 0.0172028 * $K - 1.73364;  // Local apparent time
      $U = $T - $F;                             // Universal timer
      $V = $U + $G;                             // Wall clock time
      // Quadrant Determination
      if ($D == 0) {exit;}
      while ($V < 0)   {$V = ($V + $D);}
      while ($V >= $D) {$V = ($V - $D);}
      $V = $V * 3.81972;

      $hour = intval($V);
      $min  = intval((($V - $hour) * 60) + 0.5);

      echo "<font size=\"1\" color=\"#ff0000\">sun$type: ";
      echo date( "g:i A", mktime($hour,$min,0,$mon,$mday,$year) );
      echo "</font><br>";
    }
  }
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