Core PHP Programming, Third Edition

25.3. Bar Graphs

Bar graphs are a good way to compare values to each other. Creating them is a relatively simple task because each data point is a rectangle. The height of the rectangle represents the value of the data point. To make the transition, a scaling factor is used. In Listing 25.3 the graph is 200 pixels tall and the scaling factor is two. This means that a data point with the value 75 will be 150 pixels tall. The output is shown in Figure 25.3.

Listing 25.3. Creating a bar graph

<?php /* ** Bar graph */ //fill in graph parameters $GraphWidth = 400; $GraphHeight = 200; $GraphScale = 2; $GraphFont = 5; $GraphData = array( "Beef"=>"99", "Pork"=>"75", "Chicken"=>"15", "Lamb"=>"66", "Fish"=>"22"); //create image $image = imagecreate($GraphWidth, ...