What kind of file types does PHP getimagesize() return?

Execute this:

print_r(get_defined_constants());

And then look for constants prefixed with IMAGETYPE_. On my PHP 5.3 installation I got these values:

[IMAGETYPE_GIF] => 1
[IMAGETYPE_JPEG] => 2
[IMAGETYPE_PNG] => 3
[IMAGETYPE_SWF] => 4
[IMAGETYPE_PSD] => 5
[IMAGETYPE_BMP] => 6
[IMAGETYPE_TIFF_II] => 7
[IMAGETYPE_TIFF_MM] => 8
[IMAGETYPE_JPC] => 9
[IMAGETYPE_JP2] => 10
[IMAGETYPE_JPX] => 11
[IMAGETYPE_JB2] => 12
[IMAGETYPE_SWC] => 13
[IMAGETYPE_IFF] => 14
[IMAGETYPE_WBMP] => 15
[IMAGETYPE_JPEG2000] => 9
[IMAGETYPE_XBM] => 16
[IMAGETYPE_ICO] => 17
[IMAGETYPE_UNKNOWN] => 0
[IMAGETYPE_COUNT] => 18

As you can see Flash SWF are considered images, and actually getimagesize() is able to read the width and height of a SWF object. To me it seemed like a curiosity when I first discovered it, that's why mentioned it here.

As previously mentioned constants which start with IMAGETYPE in get_defined_constants() list supported image types.

However, if you Just run this and it will tell you which ones are supported:

function imageTypes () {

    $imageTypes = array();

    foreach(get_defined_constants() as $key => $value){
        $keyStart = explode('_', $key);
        if($keyStart[0] == 'IMAGETYPE'){
             array_push($imageTypes, $key);
        }
    }
    return $imageTypes;
}

echo "<pre>";
var_dump(imageTypes());
echo "</pre>";

That index contains the value of one of PHP's IMAGETYPE_XXX constants. An entire list of them can be found on that page, towards the bottom. That page doesn't provide the actual INT value of each one but you should be able to print a few to get the values as necessary. You could also do a comparison check if you're looking for a specific one:

if ($imageinfo[2] == IMAGETYPE_IFF) {
  // Code here
}

Quoting the manual :

Index 2 is one of the IMAGETYPE_XXX constants indicating the type of the image.

And you can find those constants onh this page, amongst the other defined by GD