Which of the following is not a predefined constant?

Which regular expression can check the validity of an e-mail addresss?

What is 'empty()'?

Which is not a valid DOM method in PHP?

What's the output? '; print_r($item); echo ''; ?>

Which is false about cURL?

What's the output? $array1 = array('a' => 'green', 'b' => 'brown', 'c' => 'blue', 'red'); $array2 = array('a' => 'green', 'yellow', 'red'); $result = array_diff_assoc($array1, $array2); print_r($result);

Is it possible to initiate abstract class?

What's the output? function cube($n) { return($n * $n * $n); } $a = array(1, 2, 3, 4, 5); $b = array_map('cube', $a); print_r($b);

Which function makes keys from array to become values and values from array to become keys?

What does DRY stand for?