Re: [RFC] Implicit isset() in Shorthand Ternary Operator

Matthew Fonda wrote (on 17/09/2014):

Hi Andrea, This is great -- thanks to you and Nikita for the work here. Syntax wise, I would prefer a function-like syntax, e.g. coalesce($a, $b, 'c') or ifsetor() instead of $a ?? $b ?? 'c'. I find this more readable, and it avoids any possible confusion about precedence within the expressions. Either way, still +1 for this feature.

Funnily enough, the standard library at my workplace has long included a coalesce() function as below, which is indeed very handy; there is also a coalesce_empty(), which calls empty($arg) instead of is_null($arg). Both pre-date the shorthand ?: operator, which could replace coalesce_empty(); the proposed ?? could replace coalesce() As mentioned in the PHPDoc, the downside of a function is that it can't short-cut evaluation if the first argument passes, whereas an operator can. It would be possible to work around this by defining a special "language construct" rather than a real function, but that's probably more confusing than it's worth. The special case for $first is a performance optimisation because func_get_args() has rather a lot of overhead; I'm guessing 5.6's variadic signatures ($args...) are less painful (can anyone confirm?) /** * coalesce * PHP analogue of the SQL Coalesce() function * @param an arbitrary number of arguments * @return the first argument which is not NULL; If all arguments are NULL, will return NULL * * coalesce( $a, $b ) is equivalent to ($a === NULL ? $a : $b) * but coalesce( hard_work(), 'default' ) only has to do hard_work() once * [OTOH, coalesce( $a, hard_work() ) has to do hard_work() even if the result gets thrown away] */ function coalesce($first) {

    if (!is_null($first))
    {
        return $first;
    }

    foreach ( func_get_args() as $arg )
    {
        if ( ! is_null($arg) )
        {
            return $arg;
        }
    }

} -- Rowan Collins [IMSoP]