highlight multiple keywords in search

i'm using this code to highlight search keywords:

function highlightWords($string, $word)
 {

        $string = str_replace($word, "<span class='highlight'>".$word."</span>", $string);
    /*** return the highlighted string ***/
    return $string;

 }

 ....

  $cQuote =  highlightWords(htmlspecialchars($row['cQuotes']), $search_result);

however, this highlights only one keyword. if the user enters more than one keyword, it will narrow down the search but no word is highlighted. how can i highlight more than one word?

Solution 1:

regular expressions is the way to go!

function highlight($text, $words) {
    preg_match_all('~\w+~', $words, $m);
    if(!$m)
        return $text;
    $re = '~\\b(' . implode('|', $m[0]) . ')\\b~';
    return preg_replace($re, '<b>$0</b>', $text);
}

$text = '
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat.
';

$words = 'ipsum labore';

print highlight($text, $words);

To match in a case-insensitive manner, add 'i' to the regular expression

    $re = '~\\b(' . implode('|', $m[0]) . ')\\b~i';

NB: for non-enlish letters like "ä" the results may vary depending on the locale.

Solution 2:

PHP > 5.3.0, try preg_filter()

/**
 * Highlighting matching string
 * @param   string  $text           subject
 * @param   string  $words          search string
 * @return  string  highlighted text
 */
public function highlight($text, $words) {
    $highlighted = preg_filter('/' . preg_quote($words, '/') . '/i', '<b><span class="search-highlight">$0</span></b>', $text);
    if (!empty($highlighted)) {
        $text = $highlighted;
    }
    return $text;
}