抓取給定關鍵字前後的x個單詞數？

Question

如何在PHP中的字符串中獲取給定關鍵字之前和之後的單詞數量[x]？我試圖從爲關鍵字定製的mysql查詢結果標記爲片段。

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 />'; 

但是，如果單詞出現多次，您希望發生什麼？或者如果這個詞沒有出現在字符串中？

編輯

getWords2的擴展版本，返回到關鍵字的出現集數

$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));