# Get value if set, or default

- Thread: https://externals.io/message/4072
- Original archive: https://news-web.php.net/php.internals/4072
- Started by Griggs Domler on 2003-08-18T21:03:08+00:00
- Messages: 4
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## #4072 — Griggs Domler — 2003-08-18T21:03:08+00:00

URL: https://externals.io/message/4072#4072

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.

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## #4073 — Robert Cummings — 2003-08-18T21:26:35+00:00

URL: https://externals.io/message/4072#4073 · In reply to: #4072

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.



> 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.
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:---------------------------------------------:
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## #4074 — Guy N. Hurst — 2003-08-18T21:48:28+00:00

URL: https://externals.io/message/4072#4074 · In reply to: #4073

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.
> 
> 
> 
> 
> > […]
> 



-- 
Guy Hurst
Senior Developer
Web Teks, Inc.
http://www.webteks.com
Phone: 757.578.4923
Toll free: 877.Web.Teks
Fax: 757.578.4996

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## #4075 — Derick Rethans — 2003-08-18T21:53:38+00:00

URL: https://externals.io/message/4072#4075 · In reply to: #4074

> Hi,
> 
> The function Robert proposes only works for going one key deep.

Can you please keep discussions to php-general@ please.

Derick

-- 
"Interpreting what the GPL actually means is a job best left to those
                    that read the future by examining animal entrails."
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