How to get MIME-type of an image with file_get_contents in PHP

Question

I need to get the MIME type of an image, but I only have the body of the image which I've got with file_get_contents. Is there a possibility to get the MIME type?

Answer 1

Yes, you can get it like this.

$file_info = new finfo(FILEINFO_MIME_TYPE);
$mime_type = $file_info->buffer(file_get_contents($image_url));
echo $mime_type;

Answer 2

If you download a file using HTTP, do not guess (aka autodetect) the MIME type. Even if you downloaded the file using file_get_contents, you can still access HTTP headers.

Use $http_response_header to retrieve headers of the last file_get_contents call (or any call with http[s]:// wrapper).

$contents = file_get_contents("https://www.example.com/image.jpg");
$pattern = "/^content-type\s*:\s*(.*)$/i";
if (($header = array_values(preg_grep($pattern, $http_response_header))) &&
    (preg_match($pattern, $header[0], $match) !== false))
{
    $content_type = $match[1];
    echo "Content-Type is '$content_type'\n";
}

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Resort to the autodetections only if the server fails to provide the Content-Type (or provides only a generic catch-all type, like application/octet-stream).