Generate uniform contents

Problem/Motivation

The Meta tags module should generate uniform contents. By uniform contents, I mean exactly the same contents as everywhere else. For example, applying relevant filter modules on fields used for tags generation.

To get an idea of what I am requesting, please proceed as follow:

1. Enable the PHP Filter module
2. Edit/create a text format using the PHP Filter module
3. Edit/create a node with a body, using the Text Format mentioned above for the body
4. In the summary of the body, write some PHP code that outputs some contents, for example:
   echo 'Hello world!';
5. In the Meta tags tab, make sure the description is set to [node:summary]
6. Save your changes
7. Look at the HTML source of the page. Instead of being executed by the PHP Filter module, the PHP code has been escaped as if it was plain HTML. You will see something like: <meta name="description" content="&lt;?php echo 'Hello world!'; ?&gt;"> instead of the expected <meta name="description" content="Hello world!">

Proposed resolution

The Meta tags module should make use of the same code than the rest of the system to get the same generated contents. In all cases, strip_tags must be maintained on the generated value since we cannot have HTML tags inside HTML attributes and the <title> element.