PHP中文关键词匹配

　　　关键词匹配是比较常见的需求，如留言、弹幕及游戏聊天中的敏感词过滤，都需要对一段文字进行关键词匹配。提取到关键词后，再做进一步处理。

本类借助PHP高效的数组和mbstring扩展，来实现对中文关键词的匹配。主要思想是以关键词为key，构建字典数组，这样便可以对每个关键词可实现常数级别的查找。

具体代码如下：

 class WordMatcher {
     public $dict = [];
     public $wordMaxLen = 0;

     function __construct(){
         if(! extension_loaded('mbstring')) {
             exit('extension mbstring is not loaded');
         }
     }

     function addWord($word) {
         $len = mb_strlen($word, 'utf-8');
         $this->wordMaxLen = $len > $this->wordMaxLen ? $len : $this->wordMaxLen;
         $this->dict[$word] = 1;
     }

     function removeWord($word) {
         unset($this->dict[$word]);
     }

     function match($str, &$matched, $matchAll=false) {
         if(mb_strlen($str) < 1) {
             return;
         }

         $matchLen = 0;
         $len = $this->wordMaxLen;
         while($len>0) {
             $substr = mb_substr($str, 0, $len, 'utf-8');
             if(isset($this->dict[$substr])) {
                 $matchLen = $len;
                 $matched[] = $substr;
                 break;
             } else {
                 $len--;
             }
         }

         if(!$matchAll && $matchLen) {
             $str = mb_substr($str, $matchLen, null, 'utf-8');
         } else {
             $str = mb_substr($str, 1, null, 'utf-8');
         }

         $this->match($str, $matched, $matchAll);
     }
 }

 $matcher = new WordMatcher;
 $matcher->addWord('PHP');
 $matcher->addWord('语言');
 $matcher->addWord('H');

 $matcher->match('PHP是最好的语言', $matched);