How would you fall back on the default value of 'Unknown', if a request-parameter is missing or empty?

When passing an object to json_encode(), the default behavior can be modified by:

Which does not have a resource for a return type?

'virtual()' in PHP

How to get the number of arguments passed to a PHP function?

$a = array('a' => 0, 'b' => 0, 'c' => 1, 'd' => 2); $b = array_flip($a); var_dump($b); What does the 'var_dump' function show ?

What is the output?

What is the output?

Which will return the complete URL of the requested PHP page?

Is the following code valid?

Which will not return an array containing all normal Latin alphabet characters (A-Z)?