PHP Chart Library with ability to style background

I am needing to set 3 color variants of the background of a line chart along the y-axis of a chart as (low=yellow, medium=orange and high=red). Many offer background images, ability to change single background color, alternating rows, etc..开发者_Go百科. Is there a charting library for php that allows for that level of customization along the y-axis.

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Have you considered the Google Charts API?

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This will do...

http://code.google.com/p/mtchart/