The code below uses colors from "hans at lintoo dot dk"'s note. It delivers pie charts with labels:
<?php
$bright_list = array(
    array(255, 203, 3),
    array(220, 101, 29),
    array(189, 24, 51),
    array(214, 0, 127),
    array(98, 1, 96),
    array(0, 62, 136),
    array(0, 102, 179),
    array(0, 145, 195),
    array(0, 115, 106),
    array(178, 210, 52),
    array(137, 91, 74),
    array(82, 56, 47)
);
$dark_list = array(
    array(205, 153, 0),
    array(170, 51, 0),
    array(139, 0, 1),
    array(164, 0, 77),
    array(48, 0, 46),
    array(0, 12, 86),
    array(0, 52, 129),
    array(0, 95, 145),
    array(0, 65, 56),
    array(128, 160, 2),
    array(87, 41, 24),
    array(32, 6, 0)
);
$data = array();
$angle = array();
$title = array();
$i = 0;
foreach( $_GET as $key => $value ) {
    $data[$i] = intval($value);
    $title[$i++] = str_replace("_"," ",strval($key));
}
$sum = array_sum($data);
if( $sum == 0 ) {
    ++ $sum;
}
$count = count($data);
for( $i = 0; $i < $count; ++ $i ) {
    $angle[$i] = floor($data[$i]/$sum*360);
    if( $angle[$i] == 0 ) {
        ++ $angle[$i];
    }
}
$sum_angle = array_sum($angle);
if( $sum_angle < 360 ) {
    $angle[0]+=360-$sum_angle;
}
$height = $count*34;
if( $height < 180 ) {
    $height = 180;
}
$im  = imagecreate (350, $height);
$background = imagecolorallocate($im, 226, 226, 226);
$border = imagecolorallocate($im,97,97,97);
$font_color = imagecolorallocate($im,0,0,0);
$font = 'yourfont.ttf';
$bright = array();
foreach( $bright_list as $c ) {
    $bright[] = imagecolorallocate($im,$c[0],$c[1],$c[2]);
}
$dark = array();
foreach( $dark_list as $c ) {
    $dark[] = imagecolorallocate($im,$c[0],$c[1],$c[2]);
}
$tmp = 0;
for( $i =0; $i < $count; ++ $i ) {
    for( $j = 100; $j > 90; -- $j ) {
        imagefilledarc($im, 100, $j, 180, 120, $tmp, $tmp+$angle[$i], $dark[$i], IMG_ARC_PIE);
    }
    $tmp += $angle[$i];
}
$tmp = 0;
for( $i =0; $i < $count; ++ $i ) {
    imagefilledarc($im, 100, 90, 180, 120, $tmp, $tmp+$angle[$i], $bright[$i], IMG_ARC_PIE);
    $tmp += $angle[$i];
}
for( $i = 0; $i < $count; ++ $i ) {
    imagefilledrectangle($im, 209, 19+($i*30), 231, 41+($i*30), $border);
    imagefilledrectangle($im, 210, 20+($i*30), 230, 40+($i*30), $bright[$i]);
    imagefttext($im, 11, 0, 240, 34+($i*30), $font_color, $font, $title[$i]);
}
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>
try 'pie.php?foo=3&bar=4&baz=6'