How PHP determines whether a GIF picture is a dynamic picture (animation)

How do I use PHP to determine if a GIF picture is a dynamic picture (animation)? The first thought is to use the getimagesize () function to look at the type value, found that all are gif, so this method is not feasible. The following is a function that the author sees on the internet to determine whether a GIF is a moving graph. Post it and share it with you.

 * * To determine whether the picture is a dynamic picture (animation)/
function Isanimatedgif ($filename) {
	$fp =fopen ($filename, ' RB ');
	$filecontent =fread ($fp, FileSize ($filename));
	Fclose ($FP);
	Return Strpos ($filecontent, Chr (0x21). chr (0xff). chr (0x0b). ' NETSCAPE2.0 ') ===false?0:1;
}

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