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 use getimagesize It does not require the GD image library and it returns same information about image type. http://it2.php.net/manual/en/function.getimagesize.php

Answer 2

Try looking at exif_imagetype

Answer 3

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
}

Answer 4

You can use the Fileinfo extension: http://www.php.net/manual/en/function.finfo-file.php

finfo_file() uses magic bytes and does not have to load the whole image into memory. The result is a string with the corresponding MIME type, e.g.:

• text/html
• image/gif
• application/vnd.ms-excel

Answer 5

Look at image magic identify. http://www.imagemagick.org/script/identify.php

The php wrapper is here: http://www.php.net/manual/en/function.imagick-identifyimage.php

Or if you just want to validate that it's an image (and don't care about the meta data): http://www.php.net/manual/en/function.imagick-valid.php

Answer 6

If you have the GD2 extension enabled, you could just use that to load the file as an image, then if it returns invalid you can catch the error and return FALSE, otherwise return TRUE.