There is a function getimagesize() at PHP which takes the file name as parameter, and returns a list that contains four values. The values are image width, image height, image type, and image attributes.
Here is the small piece of example how to use the function getimagesize(), you can check for more about the function from your php manual.
// point your image file
$file_name = "img.jpg";
// get the image information using getimagesize function.
list($img_width, $img_height, $img_type, $img_attr) = getimagesize($file_name);
print "$img_width, $img_height, $img_type, $img_attr\n";
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