本文實例講數實現從一個文本字符串中提取關鍵字的方法。分享給大家供大家參考。具體分析如下：

這是一個函數定位接收一個字符串作為參數（連同其他配置可選參數），并且定位該字符串中的所有關鍵字（出現最多的詞），返回一個數組或一個字符串由逗號分隔的關鍵字。功能正常工作，但我正在改進，因此，感興趣的朋友可以提出改進意見。

/**

* Finds all of the keywords (words that appear most) on param $str

* and return them in order of most occurrences to less occurrences.

* @param string $str The string to search for the keywords.

* @param int $minWordLen[optional] The minimun length (number of chars) of a word to be considered a keyword.

* @param int $minWordOccurrences[optional] The minimun number of times a word has to appear

* on param $str to be considered a keyword.

* @param boolean $asArray[optional] Specifies if the function returns a string with the

* keywords separated by a comma ($asArray = false) or a keywords array ($asArray = true).

* @return mixed A string with keywords separated with commas if param $asArray is true,

* an array with the keywords otherwise.

*/

function extract_keywords($str, $minWordLen = 3, $minWordOccurrences = 2, $asArray = false)

{

function keyword_count_sort($first, $sec)

{

return $sec[1] - $first[1];

}

$str = preg_replace('/[^//w0-9 ]/', ' ', $str);

$str = trim(preg_replace('//s+/', ' ', $str));

$words = explode(' ', $str);

$keywords = array();

while(($c_word = array_shift($words)) !== null)

{

if(strlen($c_word) <= $minWordLen) continue;

$c_word = strtolower($c_word);

if(array_key_exists($c_word, $keywords)) $keywords[$c_word][1]++;

else $keywords[$c_word] = array($c_word, 1);

}

usort($keywords, 'keyword_count_sort');

$final_keywords = array();

foreach($keywords as $keyword_det)

{

if($keyword_det[1] < $minWordOccurrences) break;

array_push($final_keywords, $keyword_det[0]);

}

return $asArray ? $final_keywords : implode(', ', $final_keywords);

}

//How to use

//Basic lorem ipsum text to extract the keywords

$text = "

Lorem ipsum dolor sit amet, consectetur adipiscing elit.

Curabitur eget ipsum ut lorem laoreet porta a non libero.

Vivamus in tortor metus. Suspendisse potenti. Curabitur

metus nisi, adipiscing eget placerat suscipit, suscipit

vitae felis. Integer eu odio enim, sed dignissim lorem.

In fringilla molestie justo, vitae varius risus lacinia ac.

Nulla porttitor justo a lectus iaculis ut vestibulum magna

egestas. Ut sed purus et nibh cursus fringilla at id purus.

";

//Echoes: lorem, suscipit, metus, fringilla, purus, justo, eget, vitae, ipsum, curabitur, adipiscing

echo extract_keywords($text);

希望本文所述對大家的php程序設計有所幫助。