You could try with this for mime type
$image = getimagesize($_FILES['image']['tmp_name']);
$image['mime']
will return the mime type.
This function doesn't require GD library. You can find the documentation here.
This returns the mime type of the image.
Some people use the $_FILES["file"]["type"]
but it's not reliable as been given by the browser and not by PHP.
You can use pathinfo()
as ThiefMaster suggested to retrieve the image extension.
First make sure that the image is being uploaded successfully while in development before performing any operations with the image.