An updated is_ani based on issues reported here and elsewhere
<?php
function is_ani($filename) {
if(!($fh = @fopen($filename, 'rb')))
return false;
$count = 0;
//an animated gif contains multiple "frames", with each frame having a
//header made up of:
// * a static 4-byte sequence (\x00\x21\xF9\x04)
// * 4 variable bytes
// * a static 2-byte sequence (\x00\x2C) (some variants may use \x00\x21 ?)
// We read through the file til we reach the end of the file, or we've found
// at least 2 frame headers
while(!feof($fh) && $count < 2) {
$chunk = fread($fh, 1024 * 100); //read 100kb at a time
$count += preg_match_all('#\x00\x21\xF9\x04.{4}\x00(\x2C|\x21)#s', $chunk, $matches);
}
fclose($fh);
return $count > 1;
}
?>