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);
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