Can't obtain value of $filterAt within array_walk() function within method

[comp.lang.php]

[PHP]
/**
* Filter results according to given instruction
*
* @access private
* @param object $result (reference)
* @return object $filteredResult
*/
function &filterResults(&$result) { // STATIC OBJECT ARRAY
METHOD
global $section;
list($willFilterByLetter, $letter) =
array($_REQUEST['willFilterByLetter'], $_REQUEST['letter']);
if ($willFilterByLetter && preg_match('/[a-z]/i', $letter)) {
$filterAt = $this->filterAtArray[$section];
array_walk($result, create_function('&$a', 'global $filterAt,
$letter; if (!preg_match("/^$letter/i", $a->$filterAt)) unset($a);'));
}
return $result;
}
[/PHP]

I can't obtain $filterAt within the create_function()-created function
within array_walk(), yet I can obtain $letter. I verified this via
using print_r to show that $letter exists while $filterAt does not,
however, $filterAt DOES exist prior to array_walk().

Could someone tell me what I did wrong?

Thanx
Phil

[comp.lang.php]

I found it, but I absolutely don't like it. You apparently cannot use
unset() within array_walk(), which I personally think is inefficient
since other languages, including Java, do this very same thing.

I had to do a primitive brute-force method:

/**
* Filter results according to given instruction
*
* @access private
* @param object $result (optional)
* @return object $filteredResult
*/
function &filterResults($result = '') { // STATIC OBJECT
ARRAY METHOD
global $section;
list($willFilterByLetter, $letter) =
array($_REQUEST['willFilterByLetter'], $_REQUEST['letter']);
if (is_array($result) && @sizeof($result) > 0 && $willFilterByLetter
&& strlen($letter) == 1 && ctype_alpha($letter)) {
$filterAt = $this->getFilterAtArray($section); // ONLY RETRIEVE
THE VALUE OF $this->filterAtArray[$section]
$filteredResult = array();
for ($i = 0; $i < @sizeof($result); $i++)
if (strpos(strtolower($result[$i]->$filterAt), strtolower($letter))
=== 0) array_push($filteredResult, $result[$i]);
@reset($filteredResult);
}
return $filteredResult;
}

Phil