PHP生成条形图的方法

　　<?php

　　// create an array of values for the chart. These values

　　// could come from anywhere, POST, GET, database etc.

　　$values = array(23,32,35,57,12,3,36,54,32,15,43,24,30);

　　// now we get the number of values in the array. this will

　　// tell us how many columns to plot

　　$columns  = count($values);

　　// set the height and width of the graph image

　　$width = 300;

　　$height = 200;

　　// Set the amount of space between each column

　　$padding = 5;

　　// Get the width of 1 column

　　$column_width = $width / $columns ;

　　// set the graph color variables

　　$im        = imagecreate($width,$height);

　　$gray      = imagecolorallocate ($im,0xcc,0xcc,0xcc);

　　$gray_lite = imagecolorallocate ($im,0xee,0xee,0xee);

　　$gray_dark = imagecolorallocate ($im,0x7f,0x7f,0x7f);

　　$white     = imagecolorallocate ($im,0xff,0xff,0xff);

　　// set the background color of the graph

　　imagefilledrectangle($im,0,0,$width,$height,$white);

　　// Calculate the maximum value we are going to plot

　　$max_value = max($values);

　　// loop over the array of columns

　　for($i=0;$i<$columns;$i++)

　　{

　　// set the column hieght for each value

　　$column_height = ($height / 100) * (( $values[$i] / $max_value)

　　*100);

　　// now the coords

　　$x1 = $i*$column_width;

　　$y1 = $height-$column_height;

　　$x2 = (($i+1)*$column_width)-$padding;

　　$y2 = $height;

　　// write the columns over the background

　　imagefilledrectangle($im,$x1,$y1,$x2,$y2,$gray);

　　// This gives the columns a little 3d effect

　　imageline($im,$x1,$y1,$x1,$y2,$gray_lite);

　　imageline($im,$x1,$y2,$x2,$y2,$gray_lite);

　　imageline($im,$x2,$y1,$x2,$y2,$gray_dark);

　　}

　　// set the correct png headers

　　header ("Content-type: image/png");

　　// spit the image out the other end

　　imagepng($im);

　　?>