( string image )
imagecreatefromstring() returns an image identifier
representing the image obtained from the given string. These types
will be automatically detected if your build of PHP supports them:
JPEG, PNG, GIF, WBMP, and GD2.
An image resource will be returned on success. FALSE is returned if
the image type is unsupported, the data is not in a recognised format,
or the image is corrupt and cannot be loaded.