Which of the following functions set options in curl script?

Which functions compare the substrings of the parameters?

Which functions get a list of response headers sent (or ready to send)?

How do you get header information from a URL?

How should you filter variables before passing to header()?

Which variable type can NOT be used as a type hint?

What's the output? $integer = 5; $string = strval($integer); var_dump($string);

Which is not valid PHP code?

.......... Returns the time of sunrise for a given day / location

What is the functions unlink?

What's the output: $a = true; echo (is_null($a)) ;