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? 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?

What's the output? $a = 'b'; $b = 0; echo '${$a}';

Function to calculate the sum of values in an array