Checking if an image exists

[Anon]

Hi, in a script I have, people can post images on my site, what is the best way of finding out if the link is not real, or broken?

Thanks

[[deleted]]

I guess you mean people can put URL's on your site?

You'll have to check wether the URL does indeed contain an image-link, and not a piece of javascript that redirects your users to some kinky triple-X website.
You can use a few simple string-comparison functions, or a regexp, to make sure there's no javascript in it.

To find out wether it is a working URL you can do just one thing, and that is to fetch the url and see what you get.
You can use fsockopen to open a connectopn on port 80, then you can send a HEAD request and the remote server will give you a status code. 200 is ok, 404=not found, 500=no access etc etc.

If you also want to make sure it's an image, you'll have to download the entire file and see what you get.

a little more complex than you expected? :-)

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[Anon]

Just grab the file extension. And if it's not ".gif", ".png" or ".jpg" then reject it.

[pepe-le-pew]

Hello,

Well, if you mean that by posting images they are actually linking an image to your site, this might help.

// CHECKING IF IMAGE EXISTS
if(!@Getimagesize("http://path to the Image")){
/ THEN THE IMAGE DOESN'T EXIST, THE LINK IS BROKEN, OR THE SERVER WHERE THE IMAGE IS HOSTED IS DOWN /
// the code you want to run in this case
}else{
/ THE IMAGE DOES EXIST AND IS RETRIEVABLE /

// the code you want to run in this case
}

I hope this helps,
Denis