What is the best way to determine whether or not a

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. This question is two part: for the files which do have filenames what is the best way to determine whether or not it is an image? (Just a big long if/else if list?) Secondly, for the files which dont have extensions, how can I determine if they are images?

Answer 1

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 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

If you need a fast solution, use imagesx() and imagesy(). There is also a fast way to check large image file dimensions, by reading just a small amount of data from the file header. Explained in more detail in the following url:

http://hungred.com/useful-information/php-fastest-image-width-height/

Answer 5

The type of the image is typically going to be able to be inferenced from the header information of the file.

Answer 6

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