[PHP] generate keywords from text function

<?php

/*
PHP SCRIPT

NAME: Php generate keywords from text function

You can provide a text to this function and it will generate keywords from that. 

This makes generation of keywords automatically... so easy.

This also supports stop words i.e. the list of words that should not be in the generated keywords. Basically these are common words like is, the, I, am etc.
*/

function generateKeywordsFromText($text){
	
	
	// List of words NOT to be included in keywords
      $stopWords = array('i','a','about','an','and','are','as','at','be','by','com','de','en','for','from','how','in','is','it','la','of','on','or','that','the','this','to','was','what','when','where','who','will','with','und','the','www', "such", "have", "then");
   
   
   //Let us do some basic clean up! on the text before getting to real keyword generation work
   
      $text = preg_replace('/\s\s+/i', '', $text); // replace multiple spaces etc. in the text
      $text = trim($text); // trim any extra spaces at start or end of the text
      $text = preg_replace('/[^a-zA-Z0-9 -]/', '', $text); // only take alphanumerical characters, but keep the spaces and dashes too…
      $text = strtolower($text); // Make the text lowercase so that output is in lowercase and whole operation is case in sensitive.
   
      // Find all words
      preg_match_all('/\b.*?\b/i', $text, $allTheWords);
      $allTheWords = $allTheWords[0];
      
	  //Now loop through the whole list and remove smaller or empty words
      foreach ( $allTheWords as $key=>$item ) {
          if ( $item == '' || in_array(strtolower($item), $stopWords) || strlen($item) <= 3 ) {
              unset($allTheWords[$key]);
          }
      }   
	  
	  // Create array that will later have its index as keyword and value as keyword count.
      $wordCountArr = array();
	  
	  // Now populate this array with keywrds and the occurance count
      if ( is_array($allTheWords) ) {
          foreach ( $allTheWords as $key => $val ) {
              $val = strtolower($val);
              if ( isset($wordCountArr[$val]) ) {
                  $wordCountArr[$val]++;
              } else {
                  $wordCountArr[$val] = 1;
              }
          }
      }
	  
	  // Sort array by the number of repetitions
      arsort($wordCountArr);
	  
	  //Keep first 10 keywords, throw other keywords
      $wordCountArr = array_slice($wordCountArr, 0, 10);
	  
	  // Now generate comma separated list from the array
	  $words="";
	  foreach  ($wordCountArr as $key=>$value)
	  $words .= ", " . $key ;
	  
	  // Trim list of comma separated keyword list and return the list
      return trim($words,",");
}

echo generateKeywordsFromText("I want a simple php function that can generate keywords from any given text. Keyword generation is very important for me. I you have any such function then please refer me to this generate keywords from text function");

?>