用PHP简易实现中文分词

//词典类
class ch_dictionary {
    var $_id;

    function ch_dictionary($fname = "") {
        if ($fname != "") {
            $this->load($fname);
        }
    }

    // 根据文件名载入字典 (gdbm数据档案)
    function load($fname) {
        $this->_id = dba_popen($fname, "r", "gdbm");
        if (!$this->_id) {
            echo "failed to open the dictionary.($fname)<br>/n";
            exit;
        }
    }

    // 根据词语返回频率, 不存在返回-1
    function find($word) {
        $freq = dba_fetch($word, $this->_id);
        if (is_bool($freq)) $freq = -1;
        return $freq;
    }
}

// 分词类: (逆向)
// 先将输入的字串正向切成句子, 然后一句一句的分词, 返回由词组成的数组.
class ch_word_split {
    var $_mb_mark_list;    // 常见切分句子的全角标点
    var $_word_maxlen;    // 单个词最大可能长度(汉字字数)
    var $_dic;        // 词典...
    var $_ignore_mark;    // true or false
   
    function ch_word_split () {
        $this->_mb_mark_list = array("，","　","。","！","？","：","……","、","“","”","《","》","（","）");
        $this->_word_maxlen  = 12;    // 12个汉字
        $this->_dic = null;
        $this->_ignore_mark = true;
    }

    // 设定字典
    function set_dic($fname) {
        $this->_dic = new ch_dictionary($fname);
    }

    function set_ignore_mark($set) {
        if (is_bool($set)) $this->_ignore_mark = $set;
    }

    // 将字串切成句子再加以切分成词
    function string_split($str, $func = "") {       
        $ret = array();
       
        if ($func == "" || !function_exists($func)) $func = "";       
       
        $len = strlen($str);
        $qtr = "";

        for ($i = 0; $i < $len; $i++) {
            $char = $str[$i];

            if (ord($char) < 0xa1) {
                // 读取到一个半角字符
                if (!empty($qtr)) {
                    $tmp = $this->_sen_split($qtr);
                    $qtr = "";

                    if ($func != "") call_user_func($func, $tmp);                   
                    else $ret = array_merge($ret, $tmp);                   
                }

                // 如果是单词或数字. 根据 char 将数据读取到 >= 0xa1为止
                if ($this->_is_alnum($char)) {
                    do {
                        if (($i+1) >= $len) break;
                        $char2 = substr($str, $i + 1, 1);
                        if (!$this->_is_alnum($char2)) break;

                        $char .= $char2;
                        $i++;
                    } while (1);

                    if ($func != "") call_user_func($func, array($char));
                    else $ret[] = $char;                   
                }
                elseif ($char == ' ' || $char == "/t") {
                    // nothing.
                    continue;
                }
                elseif (!$this->_ignore_mark) {
                    if ($func != "") call_user_func($func, array($char));
                    else $ret[] = $char;                   
                }
            }
            else {
                // 双字节字符.
                $i++;
                $char .= $str[$i];
               
                if (in_array($char, $this->_mb_mark_list)) {
                    if (!empty($qtr)) {
                        $tmp = $this->_sen_split($qtr);
                        $qtr = "";

                        if ($func != "") call_user_func($func, $tmp);
                        else $ret = array_merge($ret, $tmp);
                    }

                    if (!$this->_ignore_mark) {
                        if ($func != "") call_user_func($func, array($char));
                        else $ret[] = $char;
                    }
                }
                else {
                    $qtr .= $char;
                }
            }
        }
       
        if (strlen($qtr) > 0) {
            $tmp = $this->_sen_split($qtr);

            if ($func != "") call_user_func($func, $tmp);           
            else $ret = array_merge($ret, $tmp);           
        }

        // return value
        if ($func == "") {
            return $ret;
        }
        else {
            return true;
        }
    }

    // 将句子切成词, 逆向
    function _sen_split($sen) {
        $len = strlen($sen) / 2;
        $ret = array();

        for ($i = $len - 1; $i >= 0; $i--) {
            // 如: 这是一个分词程序
           
            // 先取得最后一个字
            $w = substr($sen, $i * 2, 2);

            // 最终的词长
            $wlen = 1;
           
            // 开始逆向匹配到最大长度.
            $lf = 0; // last freq
            for ($j = 1; $j <= $this->_word_maxlen; $j++) {
                $o = $i - $j;
                if ($o < 0) break;
                $w2 = substr($sen, $o * 2, ($j + 1) * 2);
               
                $tmp_f = $this->_dic->find($w2);
                //echo "{$i}.{$j}: $w2 (f: $tmp_f)/n";
                if ($tmp_f > $lf) {
                    $lf = $tmp_f;
                    $wlen = $j + 1;
                    $w = $w2;
                }
            }
            // 根据 $wlen 将 $i 偏移了
            $i = $i - $wlen + 1;
            array_push($ret, $w);
        }

        $ret = array_reverse($ret);
        return $ret;
    }

    // 判断字符是不是 字母数字_- [0-9a-z_-]
    function _is_alnum($char) {
        $ord = ord($char);
        if ($ord == 45 || $ord == 95 || ($ord >= 48 && $ord <= 57))
            return true;
        if (($ord >= 97 && $ord <= 122) || ($ord >= 65 && $ord <= 90))
            return true;
        return false;
    }
}

// 分词后的回调函数
function call_back($ar) {   
    foreach ($ar as $tmp) {
        echo $tmp . " ";
        //flush();
    }
}

// 实例(如果没有输入就从 sample.txt中读取):
$wp = new ch_word_split();
$wp->set_dic("dic.db");

if (!isset($_request['testdat']) || empty($_request['testdat'])) {
    $data = file_get_contents("sample.txt");
}
else {
    $data = & $_request['testdat'];
}

// output
echo "<h3>简易分词演示</h3>/n";
echo "<hr>/n";
echo "分词结果(" . strlen($data) . " chars): <br>/n<textarea cols=100 rows=10>/n";

// 设定是否忽略不返回分词符号(标点,常用字)
$wp->set_ignore_mark(false);

// 执行切分, 如果没有设置 callback 函数, 则返回由词组成的array
$wp->string_split($data, "call_back");

$time_end = getmicrotime();
$time = $time_end - $time_start;

echo "</textarea><br>/n本次分词耗时: $time seconds <br>/n";
?>
<hr>
<form method=post>
您也可以在下面文本框中输入文字，提交后试验分词效果:<br>
<textarea name=testdat cols=100 rows=10></textarea><br>
<input type=submit>
</form>
<hr>
附: <br>
<li>本程序源码: <a href="chinese_segment.phps">chinese_segment.php</a> (简易实现方式)</li>
<li>需要的字典: <a href="dic.db">dic.db</a> (gdbm格式)</li>

附：
（简易中文分词实现完整代码及字典下载）
http://php.twomice.net/show_hdr.php?xname=borrg11&dname=p7srg11&xpos=19
（c版简易中文分词服务程序(cscwsd)）
http://php.twomice.net/show_hdr.php?xname=borrg11&dname=p7srg11&xpos=40