PHP contextual filters

When you want to do more advances contextual filtering you could use PHP contextual filter code.

Example:
There is a questions taxonomy with a number of questions.
There is a content type with 2 term reference fields, Raised questions and Answered questions
Under each page I want a list with links to pages that answer questions raised on the page.

To get this, create a new view with a block display.

1. Create a contextual filter, on the Answered questions field.
2. Select Provide default value.
3. Select at Type; PHP Code.
4. Use the following code:

5.   $node = node_load(arg(1));
     if($node && isset($node->field_raised_questions[LANGUAGE_NONE])) {
     	foreach($node->field_raised_questions[LANGUAGE_NONE] as $term) { 
     		$terms[] = $term['tid']; 
     	}
     	return implode('+',$terms);
     } 
     else { 
     	return; 
     }
    

6. Under More, select: Filter to items that share any term.

Here is screenshot of one of example of taxonomy.