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. 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

You can use exif_imagetype()

<?php
    $type =exif_imagetype($image);

where $type is a value

1. IMAGETYPE_GIF
2. IMAGETYPE_JPEG
3. IMAGETYPE_PNG
4. IMAGETYPE_SWF
5. IMAGETYPE_PSD
6. IMAGETYPE_BMP
7. IMAGETYPE_TIFF_II (intel byte order)
8. IMAGETYPE_TIFF_MM (motorola byte order)
9. IMAGETYPE_JPC
10. IMAGETYPE_JP2
11. IMAGETYPE_JPX
12. IMAGETYPE_JB2
13. IMAGETYPE_SWC
14. IMAGETYPE_IFF
15. IMAGETYPE_WBMP
16. IMAGETYPE_XBM
17. IMAGETYPE_ICO

From the manual:

When a correct signature is found, the appropriate constant value will be returned otherwise the return value is FALSE. The return value is the same value that getimagesize() returns in index 2 but exif_imagetype() is much faster.

Answer 2

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