怎么处理mcrypt_encrypt() 加密中文后，就显示为乱码了，还原后也是

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<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><br />
<?php<br />
header("Content-Type:text/html; charset=utf-8");<br />
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$str="床前明月光,疑是地上霜"; //被加密的内容<br />
$key="key:111"; //密匙<br />
$cipher=MCRYPT_DES;  //加密算法类型<br />
$mode=MCRYPT_MODE_ECB;  //加密算法模式<br />
$iv=mcrypt_create_iv(mcrypt_get_iv_size($cipher, $mode),MCRYPT_RAND); //初始化向量<br />
echo "加密前".$str."<br>";<br />
//加密<br />
$str_encrypt=mcrypt_encrypt($cipher,$key,$str,$mode,$iv);<br />
echo "加密后".$str_encrypt."<br>";<br />
//还原<br />
$str_decrypt=mcrypt_encrypt($cipher,$key,$str_encrypt,$mode,$iv);<br />
echo "还原".$str_decrypt."<br>";<br />
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?><br />
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