Finding the bit depth of an image

I have some images with different formats (jpg, webp, png, …). I’m coding a script (in php) to gather some infos from these images (like dimensions, resolution, bit-depth and …).
Since with php built-in functions, just for jpg format (and maybe another format), it’s possible to obtain bit-depth property of an image; I tried Imagick functions to do so.
I tried this:

        $image = new Imagick($tmpName);
        $colorspace = $image->getImageColorspace();
        $bitsPerChannel = $image->getImageDepth();
        $channels = 0;
        switch ($colorspace) {
            case Imagick::COLORSPACE_SRGB:
                $channels = 3;
                break;
            case Imagick::COLORSPACE_CMYK:
                $channels = 4;
                break;
            case Imagick::COLORSPACE_GRAY:
                $channels = 1;
                break;
        }
        
        if ($image->getImageAlphaChannel()) {
            $channels += 1; // add alpha
        }
        
        $totalBitsPerPixel = $bitsPerChannel * $channels;

But the value of $totalBitsPerPixel is different with “bit-depth” property which Windows shows in “Properties” of image.

I searched stackoverflow, googled all kind of functions, chatted with Sider(chrom), but couldn’t find the reason of this.
What I’m looking for is: Windows shows a bit-depth property for each image file. How to acquire that in php?
Giving advice would be appreciated.
I attached a sample image:

enter image description here