Get image resolution when upload image

Hi, I create a control panel for my client change some parts of his site, and one thing he can do, is upload image.
But is not all images, just images that width < height.
I need help to know how I check the resolution of image, before I safe in respective folder.
I know get 3 things of each image, name, size in bytes, and the type:
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$filename = $_FILES['uploadfile']['name'];
        $filesize =  $_FILES['uploadfile']['size'];
            $filetype =  $_FILES['uploadfile']['type'];
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I need to know because if height < width the script don't continue.....

Have a way to know the resolution of image before I save the image in folder and in data base?

Regards,
JC