Question

When attempting to calculate the keyword density of a single keyword in a string of content, the formula is pretty straightforward: kwd = (keyword count / total word count ) * 100

However, what should the formula be when we are looking for keyword density of a keyword phrase?

For example, how would you calculate the keyword density of the phrase “blue widgets” in the following string?

$myContent = "Blue widgets in a field
of widgets blue makes for lots of widgets, true. But
if a widget is blue, is it still a
\"blue widget\" or just a lone widget in a sea
of blue?";

Here’s my current function

function my_keyword_density($post)
{
    $word_count =  my_word_count($post);
    $keyword_count = my_keyword_count($post);
    $density = ($keyword_count / $word_count) * 100;
    $density = number_format($density, 1);
return $density;
}

How can I get a count of the number of words in the keyword phrase?

Answer 1

you can try something like this:

$tot_words = str_word_count($myContent);
$keyword_count = preg_match_all("/\bblue widgets\b/msiU", $myContent, $res);
$kwd = ($keyword_count / $tot_words) * 100;

If you need to customize what is considereded a “word” you can add a parameter to the str_word_count function, see the manual page. The just add error checking where needed and it should work.
About the formula, I’d use something like this:

    $search_words = str_word_count("blue widgets");
    $kwd = ($keyword_count / ($tot_words - (($keyword_count -1) * $search_words));

This way you’ll handle all the multi word keyphrase as if it’s single-worded. Hope it helps