How plugin can check if meta tag exists?

Question

So, I'm trying to modify a plugin. This plugin sets some meta tags in the head section using addCustomTag (adding <meta property="og:...>, etc.) The problem is that they should be added only once. Is it good idea to use $woo = JResponse::getBody(); and to check within with preg_match()? My concern here is that JResponse is deprecated. Event used is onContentAfterDisplay.

Answer 1

Add the entry only once by adding a field to your application and check whenever you want to add your custom tag.

$app = JFactory::getApplication();
if(!isset($app->metaloaded))
{
  $document->addCustomTag('<meta property="og:..."/>');
  $app->metaloaded = true;
}

Now if you want to call it at some other place or the function is called twice in the same request, the check will prevent it from executing twice.

To check within already existing custom tags added by other extensions, you can use the below code:

$document = JFactory::getDocument();
$headData = $document->getHeadData();
$existing = false

foreach($headData['custom'] as $tag)
{
   if($tag == $mytag) // or you can use if(strcmp($tag, $mytag) === 0))
   {
       $existing = true;
       break;
   }
}

// now if the tag does not exist, add your tag
if(!$existing)
{
    // add your tag here
}