php/jquery - check if image in url really exists

Question

I found this nifty way to check if a page really exists:

$headers=@get_headers($imageurl);
if(strpos($headers[0],'200')===false){
    echo "not valid";
    exit;
}

What I need to achieve, though, is to check whether on that page is really only an image. For example, when you try the following link: www.google.com/image.jpg it will return 200 because Google has it's own error page - however, it should be possible to find out not only that there is no image on that page, but also that an image is not the only thing on that page, even when there is other content (like here: http://www.kapstadt-entdecken.de/wp-content/gallery/robben-island/1robben-island.jpg).

How I can I achieve that?

Thanks a lot!

Dennis

Ja͢ck · Accepted Answer · 2012-05-07 18:51:00Z

1

You will probably want to use HEAD requests when getting headers (it doesn't do that by default):

stream_context_set_default(array(
    'http' => array(
        'method' => 'HEAD'
    )
));

Second, you can pass a second parameter to get_headers to parse it for you:

$headers = get_headers($imageurl, 1);

Then, you can check the rest as per normal:

if (strpos($headers[0], '200') === false) {
    echo "not valid";
    exit;
}

if (isset($headers['Content-Type']) && 0 === strncmp($headers['Content-Type'], 'image/', 6)) {
    echo "valid image";
} else {
    echo "probably not an image";
}

answered May 7, 2012 at 18:51

Ja͢ck

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5 Comments

Dennis Hackethal Over a year ago

I only need to check if it doesn't work, so I changed it to: if (!isset($headers['Content-Type']) && 0 === strncmp($headers['Content-Type'], 'image/', 6)) { echo "not valid"; exit; } doesn't work unfortunately...

Ja͢ck Over a year ago

The inverse is !isset($headers['Content-Type']) || 0 !== strncmp($headers['Content-Type'], 'image/', 6)

Dennis Hackethal Over a year ago

no I was mistaken. it works like a charm. although the inverse only works like this apparently: if(!isset($headers['Content-Type']) && 0 === strncmp($headers['Content-Type'], 'image/', 6))

Dennis Hackethal Over a year ago

but I agree that it should actually be || 0 !=

Ja͢ck Over a year ago

You should var_dump($headers); to find out why this happens, because your inverted logic is wrong, that shouldn't work.

Mihai Iorga · Accepted Answer · 2012-05-07 18:43:20Z

0

also with get_headers ... one of them will be

image/png
image/jpeg
image/gif

so

$isImage = false;
foreach($headers as $header){
    if(strpos($header,'image/')==true){
        $isImage = true;
    }
}

answered May 7, 2012 at 18:43

Mihai Iorga

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Comments

xtopher · Accepted Answer · 2012-05-07 18:54:15Z

0

$headers = @get_headers($imageurl);

$is_image = false;
foreach ($headers as $header) {
    if (strpos($header, 'Content-Type: image/') === 0) {
        $is_image = true;
        break;
    }
}

edited May 7, 2012 at 18:54

answered May 7, 2012 at 18:42

xtopher

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