PHP character encoding conversion class related content

<?php
/** 字符编码转换类, ANSI、Unicode、Unicode big endian、UTF-8、UTF-8+Bom互相转换
*   Date:   2015-01-28
*   Author: fdipzone
*   Ver:    1.0
*
*   Func:
*   public  convert       转换
*   private convToUtf8    把编码转为UTF-8编码
*   private convFromUtf8  把UTF-8编码转换为输出编码
*/
class CharsetConv{ // class start
    private $_in_charset = null;   // 源编码
    private $_out_charset = null;  // 输出编码
    private $_allow_charset = array(&#39;utf-8&#39;, &#39;utf-8bom&#39;, &#39;ansi&#39;, &#39;unicode&#39;, &#39;unicodebe&#39;);
    /** 初始化
    * @param String $in_charset  源编码
    * @param String $out_charset 输出编码
    */
    public function __construct($in_charset, $out_charset){
        $in_charset = strtolower($in_charset);
        $out_charset = strtolower($out_charset);
        // 检查源编码
        if(in_array($in_charset, $this->_allow_charset)){
            $this->_in_charset = $in_charset;
        }
        // 检查输出编码
        if(in_array($out_charset, $this->_allow_charset)){
            $this->_out_charset = $out_charset;
        }
    }
    /** 转换
    * @param  String $str 要转换的字符串
    * @return String      转换后的字符串
    */
    public function convert($str){
        $str = $this->convToUtf8($str);   // 先转为utf8
        $str = $this->convFromUtf8($str); // 从utf8转为对应的编码
        return $str;
    }
    /** 把编码转为UTF-8编码
    * @param  String $str 
    * @return String
    */
    private function convToUtf8($str){
        if($this->_in_charset==&#39;utf-8&#39;){ // 编码已经是utf-8，不用转
            return $str;
        }
        switch($this->_in_charset){
            case &#39;utf-8bom&#39;:
                $str = substr($str, 3);
                break;
            case &#39;ansi&#39;:
                $str = iconv(&#39;GBK&#39;, &#39;UTF-8//IGNORE&#39;, $str);
                break;
            case &#39;unicode&#39;:
                $str = iconv(&#39;UTF-16le&#39;, &#39;UTF-8//IGNORE&#39;, substr($str, 2));
                break;
            case &#39;unicodebe&#39;:
                $str = iconv(&#39;UTF-16be&#39;, &#39;UTF-8//IGNORE&#39;, substr($str, 2));
                break;
            default:
                break;
        }
        return $str;
    }
    /** 把UTF-8编码转换为输出编码
    * @param  String $str
    * @return String
    */
    private function convFromUtf8($str){
        if($this->_out_charset==&#39;utf-8&#39;){ // 输出编码已经是utf-8，不用转
            return $str;
        }
        switch($this->_out_charset){
            case &#39;utf-8bom&#39;:
                $str = "\xef\xbb\xbf".$str;
                break;
            case &#39;ansi&#39;:
                $str = iconv(&#39;UTF-8&#39;, &#39;GBK//IGNORE&#39;, $str);
                break;
            case &#39;unicode&#39;:
                $str = "\xff\xfe".iconv(&#39;UTF-8&#39;, &#39;UTF-16le//IGNORE&#39;, $str);
                break;
            case &#39;unicodebe&#39;:
                $str = "\xfe\xff".iconv(&#39;UTF-8&#39;, &#39;UTF-16be//IGNORE&#39;, $str);
                break;
            default:
                break;
        }
        return $str;
    }
} // class end
?>

<?php
require "CharsetConv.class.php";
$str = file_get_contents(&#39;source/unicodebe.txt&#39;);
$obj = new CharsetConv(&#39;unicodebe&#39;, &#39;utf-8bom&#39;);
$response = $obj->convert($str);
file_put_contents(&#39;response/utf-8bom.txt&#39;, $response, true);
?>