For example, a JPG cannot hold transparency; it must have a background color of some type. However, as a tradeoff, it is what is called a "lossy" format, which means that some data will be lost when it is saved due to being compressed.
PNG, however, is saved in a "lossless" format (as-is), which means the file you see as a PNG is eye-to-eye identical to what was originally saved (in many cases, a PSD file). PNGs can be slightly compressed, but not by a lot.
A script that outputs text five lines high and in a specific color.
I felt that these three array functions were sorely lacking from PHP. They're simple to use and easy to install, and follow the general syntax of the existing array methods that are default to PHP.