imagecolorset doesn't work with alpha value

Question

The manual here states that the PNG function imagecolorset() accepts a red, green, blue and alpha value, however when I specify an alpha value PHP gives me the error:

Warning: imagecolorset() expects exactly 5 parameters, 6 given

This confuses me: The other functions that add colors to the palette like imagecolorallocate() support the alpha value correctly, and even for this function the manual states that it is supposed to.

Any ideas what could be wrong?

Answer 1

Alpha support (and its associated parameter) was added in v5.4.0, as it clearly states in the function's manpage changelog: http://php.net/imagecolorset#refsect1-function.imagecolorset-changelog

You'll have to upgrade your PHP version, or not use alpha.