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20 years ago
Even more efficiency:

The original code snippet and the following suggestions are inefficient in that they rely on the overlying php to fill vertically using loops rather than taking advantage of the underlying drawing routines. Also, this is done by repeatedly drawing filled partial elipses and circular calculations are typically expensive (PHP may use tables, I'm not sure) The original code could be rewritten as 

<?php
// Add the bottom layer.
  imagefilledarc($image, 50, 60, 100, 50, 0, 45, $darknavy, IMG_ARC_PIE);
  imagefilledarc($image, 50, 60, 100, 50, 45, 75 , $darkgray, IMG_ARC_PIE);
  imagefilledarc($image, 50, 60, 100, 50, 75, 360 , $darkred, IMG_ARC_PIE);

//Now do the joining pieces.
//Note: Precompute cosines and sines for efficiency
  $c1=50*cos(45/180*M_PI);
  $s1=25*sin(45/180*M_PI);
  $c2=50*cos(75/180*M_PI);
  $s2=25*sin(75/180*M_PI);

  $area1=array(100,60,100,50,50+$c1,50+$s1,50+$c1,60+$s1);
  $area2=array(50+$c1,50+$s1,50+$c1,60+$s1,50+$c2,60+$s2,50+$c2,50+$s2);
//Note that piece 3 goes round the corner. So we are only interested in the leftmost extent. You would need to do this programatically. Also, you do not need to make vertical parts for any segments completely at the back of the pie (in fact, not filledarcs either)
  $area3=array(50+$c2,50+$s2,50+$c2,60+$s2,0,60,0,50);

  imagefilledpolygon($image, $area1 , 4 , $darknavy);
  imagefilledpolygon($image, $area2 , 4 , $darkgray);
  imagefilledpolygon($image, $area3 , 4 , $darkred);

  imagefilledarc($image, 50, 50, 100, 50, 0, 45, $navy, IMG_ARC_PIE);
  imagefilledarc($image, 50, 50, 100, 50, 45, 75 , $gray, IMG_ARC_PIE);
  imagefilledarc($image, 50, 50, 100, 50, 75, 360 , $red, IMG_ARC_PIE);
?>

Note that the polygons are perhaps slightly inefficient. If there was an imagefilledtriangle, this code would be simpler. Given how fundamental triangles are, perhaps for a future version?

Rich
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