## Why is this an issue?

The repetition of a prefix operator (`!`, or `~`) is usually a typo. The second operator invalidates the first one:

    $a = false;
    $b = ~~$a; // Noncompliant: equivalent to "$a"

While calling `!` twice is equivalent to calling the `boolval()` function, the latter increases the code readability, so it should be preferred.

    $a = 0;
    $b = !!$a; // Noncompliant: equivalent to "boolval($a)"