Now thats just an assumption. But as far as I know imagecreatefromjpeg can only retrieve files with an .jpg and .jpeg ending. Thats why theres also a imagecreatefromJPEG -> for .JPG and .JPEG files.
Now, I might lie - but I think thats where you error occurs. I guess you can't fetch "jpg's" where the image is actually created by PHP/ -> or has an .php ending. But as I said - not sure whether I talk some bullshit here, just an theory...

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抒情編程
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