PHP如何提取给定字符串的一部分？

Question

我正在为我的网站编写一个搜索引擎，需要提取带有给定关键字和搜索结果列表中的几个单词的文本块。我的结尾是这样的：

/**
 * This function return part of the original text with
 * the searched term and few words around the searched term
 * @param string $text Original text
 * @param string $word Searched term
 * @param int $maxChunks Number of chunks returned
 * @param int $wordsAround Number of words before and after searched term
 */
public static function searchTerm($text, $word=null, $maxChunks=3, $wordsAround=3) {
        $word = trim($word);
        if(empty($word)) {
            return NULL;
        }
        $words = explode(' ', $word); // extract single words from searched phrase
        $text  = strip_tags($text);  // clean up the text
        $whack = array(); // chunk buffer
        $cycle = 0; // successful matches counter
        foreach($words as $word) {
            $match = array();
            // there are named parameters 'pre', 'term' and 'pos'
            if(preg_match("/(?P\w+){0,$wordsAround} (?P$word) (?P\w+){0,$wordsAround}/", $text, $match)) {
                $cycle++;
                $whack[] = $match['pre'] . ' ' . $word . ' ' . $match['pos'];
                if($cycle == $maxChunks) break;
            }
        }
        return implode(' | ', $whack);
    }

这个函数不能工作，但是您可以看到基本的想法。欢迎您提出任何改进正则表达式的建议！

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Answer 1

如果不使用RegEx对输入进行净化，永远不要将用户内容注入到preg_quote模式中：

http://us3.php.net/manual/en/function.preg-quote.php

Answer 2

为什么谷歌在这里没有最好的搜索引擎，我会看看他们的用具