Keyword Extractor for Dynamic Keywords in a PHP Webpage

Date: 11/05/2015, Author: Lostwake, Category: PHP Quick Reference

This script can analyze text on a page and filter out the most used words to include in the Keywords Meta Tag.

Quite useful as a fallback on pages where you wont be entering custom keywords and dont want to run into a duplicate keyword error on Webmaster Tools.

The first thing the function defines is a list of "stop" words. This is a list of words that occur quite a bit in English text and would therefore interfere with the outcome of the function. The function also uses a variant of the slug function to remove any odd characters that might be in the text.

function extractCommonWords($string){
      $stopWords = array('i','a','about','an','and','are','as','at','be','by','com','de','en','for','from','how',
      $string = preg_replace('/ss+/i', '', $string); // replace whitespace
      $string = trim($string); // trim the string
      $string = preg_replace('/[^a-zA-Z0-9 -]/', '', $string); // only take alphanumerical
 characters, but keep the spaces and dashes too…
      $string = strtolower($string); // make it lowercase
      preg_match_all('/b.*?b/i', $string, $matchWords);
      $matchWords = $matchWords[0];
      foreach ( $matchWords as $key=>$item ) {
          if ( $item == '' || in_array(strtolower($item), $stopWords) || strlen($item) <= 3 ) {
      $wordCountArr = array();
      if ( is_array($matchWords) ) {
          foreach ( $matchWords as $key => $val ) {
              $val = strtolower($val);
              if ( isset($wordCountArr[$val]) ) {
              } else {
                  $wordCountArr[$val] = 1;
      $wordCountArr = array_slice($wordCountArr, 0, 10);
      return $wordCountArr;
$text = "This is some text. This is some text. Vending Machines are great.";
$words = extractCommonWords($text);
echo implode(',', array_keys($words));

This produces the following output.


The function returns the 10 most commonly occurring words as an array, with the key as the word and the amount of times it occurs as the value. To extract the words just use the implode() function in conjunction with the array_keys() function.