php将unicode编码转为utf-8方法http://www.welefen.com/php-unicode-to-utf8.html

unicode2utf8.php

JS里将中文转为unicode编码很简单
function convert2Unicode(str) {
    return str.replace(/[\u0080-\uffff]/g,
    function($0) {
        var tmp = $0.charCodeAt(0).toString(16);
        return "\u" + new Array(5 - tmp.length).join('0') + tmp;
    });
}
function unicode2utf8($str){
        if(!$str) return $str;
        $decode = json_decode($str);
        if($decode) return $decode;
        $str = '["' . $str . '"]';
        $decode = json_decode($str);
        if(count($decode) == 1){
                return $decode[0];
        }
        return $str;
}

js将汉字转为实体字符：

function convert2Entity(str) {
    var len = str.length;
    var re = [];
    for (var i = 0; i < len; i++) {         
        var code = str.charCodeAt(i);         if (code > 256) {
            re.push('&#' + code + ';');
        } else {
            re.push(str.charAt(i));
        }
    }
    return re.join('');
}
php将实体字符转为utf-8汉字的方法：

function entity2utf8onechar($unicode_c){
    $unicode_c_val = intval($unicode_c);
    $f=0x80; // 10000000
    $str = "";
    // U-00000000 - U-0000007F:   0xxxxxxx
    if($unicode_c_val <= 0x7F){         $str = chr($unicode_c_val);     }     //U-00000080 - U-000007FF:  110xxxxx 10xxxxxx     else if($unicode_c_val >= 0x80 && $unicode_c_val <= 0x7FF){         $h=0xC0; // 11000000         $c1 = $unicode_c_val >> 6 | $h;
        $c2 = ($unicode_c_val & 0x3F) | $f;
        $str = chr($c1).chr($c2);
    }
    //U-00000800 - U-0000FFFF:  1110xxxx 10xxxxxx 10xxxxxx
    else if($unicode_c_val >= 0x800 && $unicode_c_val <= 0xFFFF){         $h=0xE0; // 11100000         $c1 = $unicode_c_val >> 12 | $h;
        $c2 = (($unicode_c_val & 0xFC0) >> 6) | $f;
        $c3 = ($unicode_c_val & 0x3F) | $f;
        $str=chr($c1).chr($c2).chr($c3);
    }
    //U-00010000 - U-001FFFFF:  11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
    else if($unicode_c_val >= 0x10000 && $unicode_c_val <= 0x1FFFFF){         $h=0xF0; // 11110000         $c1 = $unicode_c_val >> 18 | $h;
        $c2 = (($unicode_c_val & 0x3F000) >>12) | $f;
        $c3 = (($unicode_c_val & 0xFC0) >>6) | $f;
        $c4 = ($unicode_c_val & 0x3F) | $f;
        $str = chr($c1).chr($c2).chr($c3).chr($c4);
    }
    //U-00200000 - U-03FFFFFF:  111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
    else if($unicode_c_val >= 0x200000 && $unicode_c_val <= 0x3FFFFFF){         $h=0xF8; // 11111000         $c1 = $unicode_c_val >> 24 | $h;
        $c2 = (($unicode_c_val & 0xFC0000)>>18) | $f;
        $c3 = (($unicode_c_val & 0x3F000) >>12) | $f;
        $c4 = (($unicode_c_val & 0xFC0) >>6) | $f;
        $c5 = ($unicode_c_val & 0x3F) | $f;
        $str = chr($c1).chr($c2).chr($c3).chr($c4).chr($c5);
    }
    //U-04000000 - U-7FFFFFFF:  1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
    else if($unicode_c_val >= 0x4000000 && $unicode_c_val <= 0x7FFFFFFF){         $h=0xFC; // 11111100         $c1 = $unicode_c_val >> 30 | $h;
        $c2 = (($unicode_c_val & 0x3F000000)>>24) | $f;
        $c3 = (($unicode_c_val & 0xFC0000)>>18) | $f;
        $c4 = (($unicode_c_val & 0x3F000) >>12) | $f;
        $c5 = (($unicode_c_val & 0xFC0) >>6) | $f;
        $c6 = ($unicode_c_val & 0x3F) | $f;
        $str = chr($c1).chr($c2).chr($c3).chr($c4).chr($c5).chr($c6);
    }
    return $str;
}
function entities2utf8($unicode_c){
    $unicode_c = preg_replace("/\&\#([\da-f]{5})\;/es", "entity2utf8onechar('\\1')", $unicode_c);
    return $unicode_c;
}