Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:64394
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.210.43 as permitted sender)
Message-ID: <50D3A7DC.6070402@gmail.com>
Date: Fri, 21 Dec 2012 11:05:48 +1100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0
MIME-Version: 1.0
To: Christopher Jones <christopher.jones@oracle.com>
CC: internals@lists.php.net
References: <50D05CD0.8080206@php.net> <CAPwsocFVzaCZLzUc=EQMFT3Oq-jAdVhyZzds=smmvWHYZ3T6WQ@mail.gmail.com> <50D06E8B.9020807@php.net> <CAPwsocFhPbLQUGuBuEBz1Uuz=5fpyRbRWEDVNtQqKEJSkgQckg@mail.gmail.com> <50D24B4C.4070901@garfieldtech.com> <50D29483.20802@oracle.com> <50D33D6B.4060404@garfieldtech.com> <50D3A06F.5000608@oracle.com>
In-Reply-To: <50D3A06F.5000608@oracle.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] Extension for str_replace / preg_replace with arrays
From: davidkmuir@gmail.com (David Muir)

On 21/12/12 10:34, Christopher Jones wrote:
>
>
> On 12/20/2012 08:31 AM, Larry Garfield wrote:
>> On 12/19/12 10:30 PM, Christopher Jones wrote:
>>>
>>>
>>> On 12/19/2012 03:18 PM, Larry Garfield wrote:
>>>> You could likely simplify the code even further using an infinite
>>>> iterator:
>>>>
>>>> http://us1.php.net/infiniteiterator
>>>>
>>>> $result = preg_replace_callback(
>>>>      '/word/',
>>>>      function($matches) use (&$replacements_iterator) {
>>>>          return $replacements->next();
>>>>      },
>>>>      'word word word word word'
>>>> );
>>>>
>>>> --Larry Garfield
>>>>
>>>
>>> What am I missing that causes the first call to
>>> $replacements_iterator->current() to return NULL
>>> unless the iterator is rewound before use?
>>
>> Eh, nothing.  You're right, next() doesn't return an element, it just 
>> advances, so you still need the current() call.  Which seems kinda 
>> silly to me, but whatev.
>
> That is documented, so it's OK.  The curiosity (bug?) is the need to 
> call rewind():
>
> $replacements_iterator = new InfiniteIterator(new 
> ArrayIterator($replacements));
> $replacements_iterator->rewind();  // why is the rewind needed?
>
> $result = preg_replace_callback(
>     '/word/',
>     function($matches) use ($replacements_iterator) {
>         $r = $replacements_iterator->current();
>         $replacements_iterator->next();
>         return $r;
>     },
>     'word word word word word word word word'
> );
>
> In other (simple) scripts using InfiniteIterator the rewind wasn't 
> needed.
>
>


What happens if you do:
$replacements_iterator = new InfiniteIterator(new 
ArrayIterator($replacements));
var_dump($replacements_iterator->current());

If I remember correctly, when you pass a traversable into foreach, under 
the hood, it basically calls:

$iterator->rewind();
while($iterator->valid()){
     $value = $iterator->current();
     ....(foreach block)....
     $iterator->next();
}

So that might explain why it works in "(simple) scripts".

It does seem like a bug that the rewind is required though. A newly 
created iterator should already be in a rewound state so the call 
shouldn't be needed.

Cheers,
David