What is the best way to determine whether or not a file is an image in PHP?

Question

I have a sever which people can upload files to. The problem is that some of the filenames are mangled (dont have any extension) and so I cannot immediately determine file type.

Answer 1

You can try to load the image into PHP's GD library, and see if it works.

$file = file_get_contents('file');
$img = imagecreatefromstring($file);
if($img === FALSE){
  // file is NOT an image
}
else{
  // file IS an image
}