<?php

​

$data = "It is a long  and a search for lorem ipsum will uncover many web sites still in their infancy.";

​

function getKeywordFrequency( $url ){

    // Get all the html on a page

    $html = $url;//file_get_contents( $url );

​

    // Get an array of all the words

    $allWordsArray = str_word_count( strip_tags($html), 1);

    $totalAllWordsArray = count($allWordsArray);

    // Get the amount of times a word appears on the page

    $wordCount = array_count_values($allWordsArray);

    $keywords = [];

    foreach ($wordCount as $word => $index) {

      if (strlen($word) < 4) {

        unset($wordCount[$word]);

      }

    }

    arsort($wordCount);

​

    // Loop through all the word count array and work out the percentage of a word appearing on the page

    $percentageCount = [];

    foreach($wordCount as $words => $val){

        $percentageCount[$words] = number_format(($val / $totalAllWordsArray) * 100, 2);

    }

​

    return $percentageCount;

}

print_r(getKeywordFrequency( $data));

​