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## 2.7 Acknowledgments

The idea for writing this library grew out of our own need for a high quality graph drawing library for PHP. When evaluating potential existing libraries we found (at that time circa 2001) these three

1. "chart 0.3" http://quimby.gnus.org/circus/chart/chart-0.3.tar.gz, by Lars Magne Ingebrigtsen
2. "ykcee.php", http://ykcee.sourceforge.net
3. "phplot.php", http://www.phplot.com

All these libraries implements some fine graphic features but unfortunately none of those completely fulfilled our needs either for available functionality (for example none of these supported both two Y-scales, auto-scaling, and logarithmic scales), or general flexibility. We especially needed the option of two Y-scales, which none of the above packages supported. Our own preferences for design was closest to "chart 0.3" so we started by fixing some bugs in that package and adding some new features. However It was soon realized that to add all the features and flexibility we needed to "chart 0.3" it would require a complete rewrite since the original design wasn't flexible enough, especially adding a second Y-scale would require a more flexible OO architecture.

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