I just call ffmpeg on command line with php's exec(). It's working fine and pretty fast, didn't want to mess with ffmpeg-php nor installing anything. If your host supports exec() etc. probably you can do it(php safe mode off?).
E.g.:
Put ffmpeg.exe to ".../apache/domain.com/ffmpeg.exe"
Then:
<?php
$fil="c:/videos/movie.mpg";
$command="\"C:\\Progra~1\\Apache~1\\Apache2\\htdocs\\domain.com\\ffmpeg.exe -y -i ".str_replace("/","\\"."\\",$fil)." -vframes 1 -ss 1 -an -vcodec png -f rawvideo -s 160x120 thumbnails\\thumbnail_".md5($fil).".png\"";
exec($command);
?>