PHP使用GD库生成柱状图

<?php
function createImage($data, $twidth, $tspace, $height)
{
    $dataName = array();
    $dataValue = array();
    $i = 0;
    $j = 0;
    $k = 0;
    $num = sizeof($data);

    foreach ($data as $key => $val) {
        $dataName[] = $key;
        $dataValue[] = $val;
    }

    $maxnum = max($data);
    $width = ($twidth + $tspace) * $num + 4;//image's width
    $im = imagecreate($width + 40, $height + 20);
    $lineColor = imagecolorallocate($im, 12, 12, 12);
    $bgColor = imagecolorallocate($im, 255, 233, 233);
    $tColor = imagecolorallocate($im, 123, 200, 56);
    imagefill($im, 0, 0, $bgColor);
    imageline($im, 30, 0, 30, $height - 2, $lineColor);
    imageline($im, 30, $height - 2, $width + 30 - 2, $height - 2, $lineColor);
    while ($i < $num) {
        imagefilledrectangle($im, $i * ($tspace + $twidth) + 40, $height - $dataValue[$i], $i * ($tspace + $twidth) + 40 + $twidth, $height - 3, $tColor);
        imagestringup($im, 4, $i * ($tspace + $twidth) + $twidth / 2 + 30, $height - 10, $dataName[$i] . "(" . $dataValue[$i] . ")", $lineColor);
        $i++;
    }
    while ($j <= (500 / 10)) {
        imagestringup($im, 4, 2, $height - $j * 10 + 10, $j * 10, $lineColor);
        $j = $j + 10;
    }
    while ($k <= (500 / 10)) {
        if ($k != 0)
            imageline($im, 28, $height - $k * 10, 32, $height - $k * 10, $lineColor);
        $k = $k + 10;
    }

    imagepng($im);
}


header("content-type:image/png");
$data = array("Yahoo" => 100, "Google" => 260, "Microsoft" => 320, "IBM" => 250, "Sun System" => 150, "Inter" => 220);
createImage($data, 50, 25, 500);