如何在PHP中生成大多数搜索单词的摘录？

这是一个摘录功能：

    function excerpt($text, $phrase, $radius = 100, $ending = "...") {
270             if (empty($text) or empty($phrase)) {
271                 return $this->truncate($text, $radius * 2, $ending);
272             }
273     
274             $phraseLen = strlen($phrase);
275             if ($radius < $phraseLen) {
276                 $radius = $phraseLen;
277             }
278     
279             $pos = strpos(strtolower($text), strtolower($phrase));
280     
281             $startPos = 0;
282             if ($pos > $radius) {
283                 $startPos = $pos - $radius;
284             }
285     
286             $textLen = strlen($text);
287     
288             $endPos = $pos + $phraseLen + $radius;
289             if ($endPos >= $textLen) {
290                 $endPos = $textLen;
291             }
292     
293             $excerpt = substr($text, $startPos, $endPos - $startPos);
294             if ($startPos != 0) {
295                 $excerpt = substr_replace($excerpt, $ending, 0, $phraseLen);
296             }
297     
298             if ($endPos != $textLen) {
299                 $excerpt = substr_replace($excerpt, $ending, -$phraseLen);
300             }
301     
302             return $excerpt;
303         }

它的缺点是它不会尝试匹配尽可能多的搜索词,默认情况下只匹配一次.

如何实现所需的？

解决方法:

到目前为止,这里列出的代码对我没用,所以我花了一些时间思考一个算法来实现.我现在所做的工作得体,而且似乎不是性能问题 – 随意测试.结果并不像谷歌那样时髦,因为没有检测到句子的开始和结束位置.我可以添加这个,但它会更复杂,我不得不在一个功能中做这件事.如果对象操作被抽象为方法,那么它已经变得拥挤并且可以更好地编码.

无论如何,这就是我所拥有的,它应该是一个良好的开端.确定最密集的摘录,结果字符串大约是您指定的范围.我敦促对这段代码进行一些测试,因为我还没有彻底完成它.当然有问题的案例可以找到.

我也鼓励任何人改进这个算法,或者只是执行它的代码.

请享用.

// string excerpt(string $text, string $phrase, int $span = 100, string $delimiter = '...')
// parameters:
//  $text - text to be searched
//  $phrase - search string
//  $span - approximate length of the excerpt
//  $delimiter - string to use as a suffix and/or prefix if the excerpt is from the middle of a text

function excerpt($text, $phrase, $span = 100, $delimiter = '...') {

  $phrases = preg_split('/s+/', $phrase);

  $regexp = '/b(?:';
  foreach ($phrases as $phrase) {
    $regexp .= preg_quote($phrase, '/') . '|';
  }

  $regexp = substr($regexp, 0, -1) . ')b/i';
  $matches = array();
  preg_match_all($regexp, $text, $matches, PREG_OFFSET_CAPTURE);
  $matches = $matches[0];

  $nodes = array();
  foreach ($matches as $match) {
    $node = new stdClass;
    $node->phraseLength = strlen($match[0]);
    $node->position = $match[1];
    $nodes[] = $node;
  }

  if (count($nodes) > 0) {
    $clust = new stdClass;
    $clust->nodes[] = array_shift($nodes);
    $clust->length = $clust->nodes[0]->phraseLength;
    $clust->i = 0;
    $clusters = new stdClass;
    $clusters->data = array($clust);
    $clusters->i = 0;
    foreach ($nodes as $node) {
      $lastClust = $clusters->data[$clusters->i];
      $lastNode = $lastClust->nodes[$lastClust->i];
      $addedLength = $node->position - $lastNode->position - $lastNode->phraseLength + $node->phraseLength;
      if ($lastClust->length + $addedLength <= $span) {
        $lastClust->nodes[] = $node;
        $lastClust->length += $addedLength;
        $lastClust->i += 1;
      } else {
        if ($addedLength > $span) {
          $newClust = new stdClass;
          $newClust->nodes = array($node);
          $newClust->i = 0;
          $newClust->length = $node->phraseLength;
          $clusters->data[] = $newClust;
          $clusters->i += 1;
        } else {
          $newClust = clone $lastClust;
          while ($newClust->length + $addedLength > $span) {
            $shiftedNode = array_shift($newClust->nodes);
            if ($shiftedNode === null) {
              break;
            }
            $newClust->i -= 1;
            $removedLength = $shiftedNode->phraseLength;
            if (isset($newClust->nodes[0])) {
              $removedLength += $newClust->nodes[0]->position - $shiftedNode->position;
            }
            $newClust->length -= $removedLength;
          }
          if ($newClust->i < 0) {
            $newClust->i = 0;
          }
          $newClust->nodes[] = $node;
          $newClust->length += $addedLength;
          $clusters->data[] = $newClust;
          $clusters->i += 1;
        }
      }
    }
    $bestClust = $clusters->data[0];
    $bestClustSize = count($bestClust->nodes);
    foreach ($clusters->data as $clust) {
      $newClustSize = count($clust->nodes);
      if ($newClustSize > $bestClustSize) {
        $bestClust = $clust;
        $bestClustSize = $newClustSize;
      }
    }
    $clustLeft = $bestClust->nodes[0]->position;
    $clustLen = $bestClust->length;
    $padding = round(($span - $clustLen)/2);
    $clustLeft -= $padding;
    if ($clustLeft < 0) {
      $clustLen += $clustLeft*-1 + $padding;
      $clustLeft = 0;
    } else {
      $clustLen += $padding*2;
    }
  } else {
    $clustLeft = 0;
    $clustLen = $span;
  }

  $textLen = strlen($text);
  $prefix = '';
  $suffix = '';

  if (!ctype_space($text[$clustLeft]) && isset($text[$clustLeft-1]) && !ctype_space($text[$clustLeft-1])) {
    while (!ctype_space($text[$clustLeft])) {
      $clustLeft += 1;
    }
    $prefix = $delimiter;
  }

  $lastChar = $clustLeft + $clustLen;
  if (!ctype_space($text[$lastChar]) && isset($text[$lastChar+1]) && !ctype_space($text[$lastChar+1])) {
    while (!ctype_space($text[$lastChar])) {
      $lastChar -= 1;
    }
    $suffix = $delimiter;
    $clustLen = $lastChar - $clustLeft;
  }

  if ($clustLeft > 0) {
    $prefix = $delimiter;
  }

  if ($clustLeft + $clustLen < $textLen) {
    $suffix = $delimiter;
  }

  return $prefix . trim(substr($text, $clustLeft, $clustLen+1)) . $suffix;
}

（编辑：北几岛）

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