Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:4074
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Message-ID: <3F4149AC.80509@webteks.com>
Date: Mon, 18 Aug 2003 17:48:28 -0400
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.2) Gecko/20021216
MIME-Version: 1.0
To: Robert Cummings <robert@wocmud.org>
CC:  internals@lists.php.net
References: <017801c365cc$22455a10$6901a8c0@dexby> <1061241995.32231.4.camel@blobule.suds>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] Get value if set, or default
From: hurst@webteks.com ("Guy N. Hurst")

Hi,

The function Robert proposes only works for going one key deep.

That means one would have to specify getd($arr['sublevel'],$subkey),
which would then create the key 'sublevel'.
(That is assuming one has access to the parent keys)

I have addressed this in the following function:


function arr_getd(&$space,$path,$default=""){
	if (is_array($space) ):
		if (array_key_exists($path,$space) ):
			return $space[$path];
		endif;
		if($path{0}=="$"):
			$path=substr($path,1);
		endif;
		if(strpos($path,"]")>0):
			$tmp_pos = strpos($path,"[");
			if ($tmp_pos>0):
				// rep arr x[.]
				$path = '["'.substr($path,0,$tmp_pos).'"]'.substr($path,$tmp_pos);
			endif;
			return eval("return (isset(\$space$path))?\$space$path:\$default;");
		endif;
	endif;
	return $default;
}


Now, I can pass in a string representation like this:

$val = arr_getd($arr,"['sublevel']['$subkey']","default");

This allows me to control at what point the reference autovivifies the 
passed-in array space.



Unfortunately, this approach requires the use of eval in order to
access the isset() function. Coupled with the logic and string 
functions, it takes a significant performance hit.

Since I use this inside loops, I would very much appreciate a 
language-level implementation similar to isset(), which doesn't require 
that a variable be passed in as a string representation.

Is such a thing is acceptable to the majority?


Guy N. Hurst





Robert Cummings wrote:
> Why not augment the userland function to the following:
> 
> function getd( &$sourceArray, $key, $default=null )
> {
>     if( isset( $sourceArray[$key] ) )
>     {
>         return $sourceArray[$key];
>     }
> 
>     return $default;
> }
> 
> Cheers,
> Rob.
> 
> 
> On Mon, 2003-08-18 at 17:03, Griggs Domler wrote:
> 
>>It's rare to find functionality that cannot be effectively implemented
>>in userland PHP code, but this appears to be one of them.
>> 
>>The issue here is the capability to check if an array index (or
>>variable) is set, if so, return its value, or return a passed in default
>>value. This can be accomplished using if statements or the ternary
>>operator, but they quickly become tiresome for so routine a task.
>>Especially when dealing with nested associative arrays, for example:
>> 
>>$myVar =
>>(isset($_SESSION['application']['section']['page']['title']))?$_SESSION[
>>'application']['section']['page']['title']:"Default Title";
>> 
>>Wouldn't this be better:
>> 
>>$myVar =
>>getd($_SESSION['application']['section']['page']['title'],"Default
>>Title"); 
>> 
>>At first glance defining a function that will accomplish this appears
>>easy:
>> 
>>function getd($var,$default='')
>>{
>>     if(isset($var))
>>          return $var;
>>     else
>>          return $default;
>>}
>> 
>>$myVar = getd($arr['noindex']);
>> 
>>But this is not notice level compliant, producing an error if the index
>>doesn't already exist.
>> 
>>Re-writing the function to pass by reference seems to fix this at first
>>glance:
>> 
>>function getd(&$var,$default='')
>>{
>> . . .
>>}
>> 
>>$myVar = getd($arr['noindex']);
>> 
>>
>>It no longer gives a notice. But the call mentioned above will now
>>create the index mentioned, setting its value to null, which, while not
>>necessarily wrong, still means that a foreach iteration or array_keys()
>>call will show that the key now exists. (though isset() will not.)
>> 
>>Since writing a userland function to accomplish this seems impossible
>>while maintaining notice-level compliance, could this be accomplished at
>>the language level? Perhaps by adding a statement similar to isset? It
>>would seem a very helpful addition to PHP and would not need to affect
>>other language constructs.
> 



-- 
Guy Hurst
Senior Developer
Web Teks, Inc.
http://www.webteks.com
Phone: 757.578.4923
Toll free: 877.Web.Teks
Fax: 757.578.4996