How to add meta tags to a page header based on an url parameter?

Question

Hello Joomla community,

I'm forced to write a minimum Joomla (3.4.1) plugin that injects custom meta tags based on an URL parameter. It will be used to serve localized Facebook Open Graph stories.
The problem is, I have literally NO Joomla and PHP background and a VERY tight deadline! Can you please explain how this can be accomplished in a bare minimum implementation?

What I need to know is:

• What's the easiest/fastest way to create an empty Joomla (3.4.1 compatible) component?
• How can the current url be read?
• How can a custom tag be injected to the page?

If those questions are answered, I should be able to figure out the rest by myself, so please explain in as much detail as possible.

Thank you very much!

Answer 1

Assuming that with "Read Current Url", you mean that you want to be able to get request data, then:

$jinput = JFactory::getApplication()->input;
$url_parameter = $jinput->get('url_param', 'default', 'filter');

Extended Documentation with info about the filter options: Retrieving_request_data_using_JInput

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To add metadata in the head:

$document = JFactory::getDocument();
$document->setMetaData( 'tagname', 'tagcontent' );

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As for the easiest/fastest way to create an empty component, check the Hello World component:

https://github.com/joomla/Joomla-3.2-Hello-World-Component

https://docs.joomla.org/J3.x:Developing_a_MVC_Component/Developing_a_Basic_Component