In Php !null return 1? Or return Boolean true?

Question

PHP

Answer 1

<?php

error_reporting(E_ALL);

$foo = NULL;
var_dump(is_null($inexistent), is_null($foo));

?>

Notice: Undefined variable: inexistent in ... bool(true) bool(true)

https://stackoverflow.com/questions/137487/null-vs-false-vs-0-in-php

Answer 2

I see, var_dump( null == false ); so in this case !null return true