fixed possible endless loop processing png file with wrong filesize

[edanp]

I'm processing a list of files that I read from an external url and saving them with the same filename on disk (temp name only for processing). Since the library is using filesize which is cached, the png parser goes into an endless loop when dealing with a smaller file than the previous one.

I have few options to solve it outside the library like using a different name per file or calling clearstatcache before every call to the library, but I still think it should not be possible to reach an endless loop in the code.

Below is an example code that should trigger the endless loop. big-file.png should be bigger in size than small-file.png.

My fix checks that fread returns data and breaks with a warning if it returns empty.

<?php
        $target = '/tmp/tmp.png';

        // don't use PHP copy because it will clear cache
        $src = '/tmp/big-file.png';
        exec("cp $src $target");
        $getID3 = new \getID3;
        $analyze = $getID3->analyze($target);

        $src = '/tmp/small-file.png';
        exec("cp $src $target");
        $getID3 = new \getID3;
        $analyze = $getID3->analyze($target);

[JamesHeinrich]

Sorry, somehow I didn't notice this PR until just now.