Question

I am trying to remove any user inserted image tags while allowing my own image icon. I have this

$post = 'Here is an image <img src="imgage.jpg" /> to check
         and my icon <img src="/images/ImageLink.jpg" />';

$imgcheck = true;
$stringstart = 0;

while($imgcheck == 'true'){
    if($stringstart = strpos($post,'<img',$stringstart)){
        if ($stringend = strpos($post,'>',$stringstart)){
            $strlength = $stringend - $stringstart;
            $substring = substr($post,$stringstart,$strlength);
            if (!preg_match('/src="\/images\/ImageLink.jpg"/',$substring)){
                $post = str_replace($substring, "", $post);
            }
            else{
                $stringstart = $stringend;
            }

        }
        else{
            $imgcheck = 'false';
        }
    }
    else{
            $imgcheck = 'false';
    }

}

I would like this to return

Here is an image to check and my icon <img src="/images/ImageLink.jpg" />

I seem to be getting an error on one of the strpos functions but cannot figure out why.

Update:Thank you hakre. That answer is much more elegant. I did finally make the code work with

$imgcheck = true;
$stringstart = 0;

while($imgcheck == 'true'){
    if($stringstart = strpos($post,'<img',$stringstart)){
        if ($stringend = strpos($post,'>',$stringstart)){
            $strlength = $stringend - $stringstart +4;
            $substring = substr($post,$stringstart,$strlength);
            if (!preg_match('~src="\/images\/ImageLink.jpg"~',$substring)){
                $post = str_replace($substring, "", $post);
            }
            else{
                $stringstart = $stringend;
            }

        }
        else{
            $imgcheck = 'false';
        }
    }
    else{
            $imgcheck = 'false';
    }

}

with < and > used because I am using a div with contenteditable=true for user input. This could also be used for a text area by simply replacing < and > with <img and > respectively as well as changing

$strlength = $stringend - $stringstart +4;

to

$strlength = $stringend - $stringstart +1;

Thank you for your time.

Answer 1

You should use a HTML parser for the job, for example DOMDocument.

The following example code will put your html fragment into a div with the id post so it can be identified:

$post = 'Here is an image <img src="imgage.jpg" /> to check
         and my icon <img src="/images/ImageLink.jpg" />';

$post = '<div id="post">'.$post.'</div>';

Then the DOMDocument is created and the html loaded into it. Additionally the container div is made available as a variable by it’s id:

$doc = new DOMDocument();
$doc->loadHTML($post);
$container = $doc->getElementById('post');

The next step is to select all images you want to remove. This is done with xpath. The xpatch expression will then be queried with the $container as reference:

$xpath = new DOMXPath($doc);    
$expression = './/img[@src != "/images/ImageLink.jpg"]';
$nodes = $xpath->query($expression, $container);

The next step is to iterate over all found elements and to remove them:

foreach($nodes as $node)
{
    $parent = $node->parentNode;
    $parent->removeChild($node);
}

Finally the changed HTML needs to be aquired by taking everything out of the $container:

$innerHTML = '';
foreach($container->childNodes as $child) {
    $innerHTML .= $node->ownerDocument->saveXML($child);
}

Now everything is in

echo $innerHTML;

which will give you:

Here is an image  to check
         and my icon <img src="/images/ImageLink.jpg"/>

Hope this is useful.