抓取给定关键字前后的 x 个单词？

Question

如何在 PHP 字符串中抓取给定关键字前后的 [x] 个单词？我正在尝试将针对关键字定制的 mysql 查询的结果标记为片段。

Answer 1

$string = 'This is a test string to see how to grab words from an arbitrary sentence. It\'s a little hacky (as you can see from the results) - but generally speaking, it works.';

echo $string,'<br />';

function getWords($string,$word,$before=0,$after=0) {
    $stringWords = str_word_count($string,1);
    $myWordPos = array_search($word,$stringWords);

    if (($myWordPos-$before) < 0)
        $before = $myWordPos;
    return array_slice($stringWords,$myWordPos-$before,$before+$after+1);
}

var_dump(getWords($string,'test',2,1));
echo '<br />';
var_dump(getWords($string,'this',2,1));
echo '<br />';
var_dump(getWords($string,'sentence',1,3));
echo '<br />';
var_dump(getWords($string,'little',2,2));
echo '<br />';
var_dump(getWords($string,'you',2,2));
echo '<br />';
var_dump(getWords($string,'results',2,2));
echo '<br />';
var_dump(getWords($string,'works',2,2));

echo '<hr />';


function getWords2($string,$word,$before=0,$after=0) {
    $stringWords = str_word_count($string,1);
    $myWordPos = array_search($word,$stringWords);
    $stringWordsPos = array_keys(str_word_count($string,2));

    if (($myWordPos+$after) >= count($stringWords))
        $after = count($stringWords) - $myWordPos - 1;
    $startPos = $stringWordsPos[$myWordPos-$before];
    $endPos = $stringWordsPos[$myWordPos+$after] + strlen($stringWords[$myWordPos+$after]);

    return substr($string,$startPos,$endPos-$startPos);
}

echo '[',getWords2($string,'test',2,1),']<br />';
echo '[',getWords2($string,'this',2,1),']<br />';
echo '[',getWords2($string,'sentence',1,3),']<br />';
echo '[',getWords2($string,'little',2,2),']<br />';
echo '[',getWords2($string,'you',2,2),']<br />';
echo '[',getWords2($string,'results',2,2),']<br />';
echo '[',getWords2($string,'works',1,3),']<br />';

但如果这个词多次出现，你希望发生什么？或者如果该单词没有出现在字符串中？

编辑

getWords2 的扩展版本，最多返回关键字出现的设定次数

$string = 'PHP is a widely-used general-purpose scripting language that is especially suited for Web development. The current version of PHP is 5.3.3, released on July 22, 2010. The online manual for PHP is an excellent resource for the language syntax and has an extensive list of the built-in and extension functions. Most extensions can be found in PECL. PEAR contains a plethora of community supplied classes. PHP is often paired with the MySQL relational database.';

echo $string,'<br />';

function getWords3($string,$word,$before=0,$after=0,$maxFoundCount=1) {
    $stringWords = str_word_count($string,1);
    $stringWordsPos = array_keys(str_word_count($string,2));

    $foundCount = 0;
    $foundInstances = array();
    while ($foundCount < $maxFoundCount) {
        if (($myWordPos = array_search($word,$stringWords)) === false)
            break;
        ++$foundCount;
        if (($myWordPos+$after) >= count($stringWords))
            $after = count($stringWords) - $myWordPos - 1;
        $startPos = $stringWordsPos[$myWordPos-$before];
        $endPos = $stringWordsPos[$myWordPos+$after] + strlen($stringWords[$myWordPos+$after]);

        $stringWords = array_slice($stringWords,$myWordPos+1);
        $stringWordsPos = array_slice($stringWordsPos,$myWordPos+1);

        $foundInstances[] = substr($string,$startPos,$endPos-$startPos);
    }
    return $foundInstances;
}

var_dump(getWords3($string,'PHP',2,2,3));