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Subject: Re: Fwd: Re: [PHP-DEV] Re: Only variables can be passed by reference
From: rowan.collins@gmail.com (Rowan Collins)

On 04/12/2014 23:46, Chris Wright wrote:
> Forgot to cc list, see below
>
> ---------- Forwarded message ----------
> From: "Chris Wright" <cw@daverandom.com>
> Date: 4 Dec 2014 14:09
> Subject: Re: [PHP-DEV] Re: Only variables can be passed by reference
> To: "Andrea Faulds" <ajf@ajf.me>
> Cc:
>
>> On 4 December 2014 at 12:26, Andrea Faulds <ajf@ajf.me> wrote:
>>>
>>>> On 4 Dec 2014, at 10:38, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:
>>>>
>>>>
>>>> Yet another sample code. This cannot be executed on 3v4l.org for
> security
>>>> reasons.
>>>>
>>>> <?php
>>>> $sock = fsockopen('www.php.net', '80');
>>>> var_dump($sock);
>>>>
>>>> $socks = array($sock);
>>>> var_dump(stream_select($socks, $socks, $socks, 1));
>>>>
>>>> //var_dump(stream_select(array($sock), array($sock), array($sock), 1));
>>>> //Fatal error: Only variables can be passed by reference in
>>>> /home/yohgaki/tmp/ttt.php on line 8
>>>> ?>
>>> Using stream_select without real variables like that is weird, what’s
> the point? You’ve discarded the read/write/error information, all the
> return value tells you is that *something* changed.
>> While I'm undecided on this change (leaning towards "no"), there is a
> more useful example with stream_select():
>> $socks = array($sock);
>> var_dump(stream_select($socks, $socks, NULL, 1));
>>
>> It is rare that anything actually uses OOB data in the real world, more
> often than not stream_select() is preceded by a line like $e = NULL;
>> I could maybe get behind this for specifically permitting literal NULL to
> be passed, as is often the convention for out params in C, where passing a
> NULL pointer is permitted and handled as "I don't want this data".
>> Another example of where this could be useful is stream_socket_client(),
> where you want to specify timeout/flags/context but don't care about
> errno/errstr, so you could pass literal NULL to these instead of having to
> declare a couple of trash variables.
>> That said, the use cases above would probably be better served by named
> parameters.
>

Perhaps if a parameter is optional and defaulted to null, a literal null 
could be allowed even if it would normally be by-ref? This would match 
the behaviour of type-hinting, e.g.

function foo(Bar $bar=null) { ... }
foo(null);

function foo(&$bar=null) { ... }
foo(null);

The point being that you could then skip over by-ref parameters in some 
of the examples above, e.g. allow this:

$sock = fsockopen('www.php.net', '80');
$socks = array($sock);
stream_select($socks, null, null, 1);

Named parameters would make this look prettier, but you'd need to make 
the parameters optional in the declaration anyway.

-- 
Rowan Collins
[IMSoP]