how to check if a url is an image url with php?

Question

I need to check the url is image url or not? How can i do this?

Examples :

• http://www.google.com/ is not an image url.
• http://www.hoax-slayer.com/images/worlds-strongest-dog.jpg is an image url.
• https://stackoverflow.com/search?q=.jpg is not an image url.
• http://www.google.com/profiles/c/photos/private/AIbEiAIAAABECK386sLjh92M4AEiC3ZjYXJkX3Bob3RvKigyOTEzMmFmMDI5ODQ3MzQxNWQxY2VlYjYwYmE2ZTA4YzFhNDhlMjBmMAEFQ7chSa4PMFM0qw02kilNVE1Hpw is an image url.

Answer 1

Here is a way that requires curl, but is faster than getimagesize, as it does not download the whole image. Disclaimer: it checks the headers, and they are not always correct.

function is_url_image($url){
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url );
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_HEADER, 1);
        curl_setopt($ch, CURLOPT_NOBODY, 1);
        $output = curl_exec($ch);
        curl_close($ch);

        $headers = array();
        foreach(explode("\n",$output) as $line){
            $parts = explode(':' ,$line);
            if(count($parts) == 2){
                $headers[trim($parts[0])] = trim($parts[1]);
            }

        }

        return isset($headers["Content-Type"]) && strpos($headers['Content-Type'], 'image/') === 0;
    }

Answer 2

If you want to be absolutely sure, and your PHP is enabled for remote connections, you can just use

getimagesize('url');

If it returns an array, it is an image type recognized by PHP, even if the image extension is not in the url (per your second link). You have to keep in mind that this method will make a remote connection for each request, so perhaps cache urls that you already probed in a database to lower connections.