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]
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