Custom array sorting function and sorting class implemented in PHP

/*
* 二维数组自定义排序函数
* uasort($arr,function_name)
*
**/
$arr = array(
  array('a'=>1,'b'=>'c'),
  array('a'=>4,'b'=>'a'),
  array('a'=>5,'b'=>'g'),
  array('a'=>7,'b'=>'f'),
  array('a'=>6,'b'=>'e')
);
function compare_arr($x,$y){
  if($x[&#39;b&#39;]<$y[&#39;b&#39;]){
    return -1;
  }else if($x[&#39;b&#39;]>$y[&#39;b&#39;]){
    return 1;
  }else{
    return 0;
  }
}
uasort($arr,&#39;compare_arr&#39;);
foreach($arr as $a){
  echo $a[&#39;a&#39;].&#39;=>&#39;.$a[&#39;b&#39;].&#39;<br/>&#39;;
}

class multiSort
{
   var $key;  //key in your array
   //排序函数 参数依次是 数组 待排列索引 排序类型
   function run ($myarray, $key_to_sort, $type_of_sort = '')
   {
     $this->key = $key_to_sort;
     if ($type_of_sort == 'desc')
       uasort($myarray, array($this, 'myreverse_compare'));
     else
       uasort($myarray, array($this, 'mycompare'));
     return $myarray;
   }
   //正序
   function mycompare($x, $y)
   {
     if ( $x[$this->key] == $y[$this->key] )
       return 0;
     else if ( $x[$this->key] < $y[$this->key] )
       return -1;
     else
       return 1;
   }
   //逆序
   function myreverse_compare($x, $y)
   {
     if ( $x[$this->key] == $y[$this->key] )
       return 0;
     else if ( $x[$this->key] > $y[$this->key] )
       return -1;
     else
       return 1;
   }
}