Different versions and builds of GD support a variety of image types. imagetypes() provides a way to check which formats are supported. The function accepts no arguments and returns an integer bit field. See the table below for a listing of image types and their corresponding bit values.
Thus, if the value returned from imagetypes() is 12, your build of PHP supports the PNG and WBMP image formats. You can check whether the constant that correlates to the image is also defined to help determine support for that image type. In the example below using the bitwise & operator, if the value returned is 0 then no GIF support is enabled.
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