usort - more parameters

Hallo, how can I pass more parameters to usort? I have different functions, which are very similar in structure, I want to have just one function:

<?php

     $arr = array(      array('number' => 100, 'string'=>'aaa'),
            开发者_运维知识库    array('number'=>50, 'string'=>'bdef'),
                array('number'=>150, 'string'=>'cbba')
            );


    usort($arr,  'sortNumberDesc');

    //How can I use just a single function?
    //How can I pass further parameters to usort?

    function sortNumberDesc($a, $b){
       $a = $a['number'];
       $b = $b['number'];
       if ($a == $b) return 0;
       return ($a > $b) ? -1 : +1;
    }

    function sortNumberAsc($a, $b){
       $a = $a['number'];
       $b = $b['number'];  
       if ($a == $b) return 0;
       return ($a < $b) ? -1 : +1;
    }

    //I want to do the same with just one function:
    //Sort ID is the search index, reverse DESC or ASC 
    function sort($a, $b, $sortId='number', $reverse = 0){
       $a = $a[$sortId];
       $b = $b[$sortId]; 
       if ($a == $b) return 0;
       if($reverse == false) return ($a > $b) ? -1 : +1;
       else return ($a < $b) ? -1 : +1;
    }

    print_r($arr);
?>

---

You can use a much simpler function:

function sortNumberAsc($a, $ b){
       $a = $a['number'];
       $b = $ b['number'];  
       if ($a == $b) return 0;
       return ($a < $b) ? -1 : +1;
}