PHP method to implement Unicode encoding mutual conversion

<?php
/**
* $str 原始中文字符串
* $encoding 原始字符串的编码，默认utf-8
* $prefix 编码后的前缀，默认""
* $postfix 编码后的后缀，默认";"
*/
function unicode_encode($str, $encoding = &#39;utf-8&#39;, $prefix = &#39;&#39;, $postfix = &#39;;&#39;) {
 //将字符串拆分
 $str = iconv("UTF-8", "gb2312", $str);
 $cind = 0;
 $arr_cont = array();
 for ($i = 0; $i < strlen($str); $i++) {
  if (strlen(substr($str, $cind, 1)) > 0) {
   if (ord(substr($str, $cind, 1)) < 0xA1) { //如果为英文则取1个字节
    array_push($arr_cont, substr($str, $cind, 1));
    $cind++;
   } else {
    array_push($arr_cont, substr($str, $cind, 2));
    $cind+=2;
   }
  }
 }
 foreach ($arr_cont as &$row) {
  $row = iconv("gb2312", "UTF-8", $row);
 }
 //转换Unicode码
 foreach ($arr_cont as $key => $value) {
  $unicodestr.= $prefix . base_convert(bin2hex(iconv(&#39;utf-8&#39;, &#39;UCS-4&#39;, $value)), 16, 10) .$postfix;
 }
 return $unicodestr;
}
/**
* $str Unicode编码后的字符串
* $decoding 原始字符串的编码，默认utf-8
* $prefix 编码字符串的前缀，默认""
* $postfix 编码字符串的后缀，默认";"
*/
function unicode_decode($unistr, $encoding = &#39;utf-8&#39;, $prefix = &#39;&#39;, $postfix = &#39;;&#39;) {
 $arruni = explode($prefix, $unistr);
 $unistr = &#39;&#39;;
 for ($i = 1, $len = count($arruni); $i < $len; $i++) {
  if (strlen($postfix) > 0) {
   $arruni[$i] = substr($arruni[$i], 0, strlen($arruni[$i]) - strlen($postfix));
  }
  $temp = intval($arruni[$i]);
  $unistr .= ($temp < 256) ? chr(0) . chr($temp) : chr($temp / 256) . chr($temp % 256);
 }
 return iconv(&#39;UCS-2&#39;, $encoding, $unistr);
}
$str = "PHP编程：www.jb51.net";
$unistr = unicode_encode($str);
$unistr2 = unicode_decode($unistr);
echo $unistr . &#39;<br />&#39;;
echo $unistr2 . &#39;<br />&#39;;
$unistr = unicode_encode($str,&#39;GBK&#39;,&#39;\\u&#39;);
$unistr2 = unicode_decode($unistr,&#39;GBK&#39;,&#39;\\u&#39;);
echo $unistr . &#39;<br />&#39;;
echo $unistr2 . &#39;<br />&#39;;