What are some alternative methods to determine the content type of a remote URL in PHP for image validation?

When validating images from a remote URL in PHP, one common method is to check the Content-Type header of the HTTP response. However, this method can be unreliable as it can be spoofed or incorrect. An alternative method is to use the getimagesize() function in PHP, which returns an array containing the image size and type. This function can provide more accurate information about the image type, helping to validate the image more effectively.

function validateImageFromURL($url) {
    $image_info = getimagesize($url);
    
    if($image_info !== false) {
        $image_type = $image_info[2];
        
        if(in_array($image_type, [IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF])) {
            echo "Image is valid";
        } else {
            echo "Invalid image type";
        }
    } else {
        echo "Invalid image";
    }
}

// Example usage
validateImageFromURL('https://example.com/image.jpg');