25.4. Pie Charts
Pie charts are a good way to see how a value represents a percentage of a whole. Each data point is a slice of a pie with a unique color. A legend associates the colors with each data point's label and value.
Since the pie chart is round, it represents a slightly more complex problem than the bar graph. PHP's image functions allow you to draw a pie slice, solid or outlined. Because each slice represents a portion of the whole, the script must calculate how many degrees to dedicate to the slice by dividing the value by the total of all slice values. Then it's a matter of calling imagefilledarc.
As with the bar graph, the data used in the chart come from an array hardcoded into the script in Listing 25.4. It is possible to keep ...
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