php - How do I convert a string to an associative array of its keywords

Question

take this string as an example: "will see you in London tomorrow and Kent the day after tomorrow".

How would I convert this to an associative array that contains the keywords as keys, whilst preferably missing out the common words, like this:

Array ( [tomorrow] => 2 [London] => 1 [Kent] => 1)

Any help greatly appreciated.

Answer 1

I would say you could :

• split the string into an array of words
  • with explode
  • or preg_split
  • depending on the complexity you'll accept for your words separators
• use array_filter to only keep the lines (i.e. words) you want
  • the callback function will have to return false for all non-valid-words
• and, then, use array_count_values on the resulting list of words
  • which will count how many times each words is present in the array of words

---

EDIT : and, just for fun, here's a quick example :

First of all, the string, that gets exploded into words :

$str = "will see you in London tomorrow and Kent the day after tomorrow";
$words = preg_split('/\s+/', $str, -1, PREG_SPLIT_NO_EMPTY);
var_dump($words);

Which gets you :

array
  0 => string 'will' (length=4)
  1 => string 'see' (length=3)
  2 => string 'you' (length=3)
  3 => string 'in' (length=2)
  4 => string 'London' (length=6)
  5 => string 'tomorrow' (length=8)
  6 => string 'and' (length=3)
  7 => string 'Kent' (length=4)
  8 => string 'the' (length=3)
  9 => string 'day' (length=3)
  10 => string 'after' (length=5)
  11 => string 'tomorrow' (length=8)

Then, the filteting :

function filter_words($word) {
    // a pretty simple filter ^^
    if (strlen($word) >= 5) {
        return true;
    } else {
        return false;
    }
}
$words_filtered = array_filter($words, 'filter_words');
var_dump($words_filtered);

Which outputs :

array
  4 => string 'London' (length=6)
  5 => string 'tomorrow' (length=8)
  10 => string 'after' (length=5)
  11 => string 'tomorrow' (length=8)

And, finally, the counting :

$counts = array_count_values($words_filtered);
var_dump($counts);

And the final result :

array
  'London' => int 1
  'tomorrow' => int 2
  'after' => int 1

Now, up to you to build up from here ;-)
Mainly, you'll have to work on :

• A better exploding function, that deals with ponctuation (or deal with that during filtering)
• An "intelligent" filtering function, that suits your needs better than mine

Have fun !

Answer 2

You could have a table of common words, then go through your string one word at a time, checking if it exists in the table, if not, then add it to your associative array, or +1 to it if it already exists.

Answer 3

using a blacklist of words not to be included

$str = 'will see you in London tomorrow and Kent the day after tomorrow';
$skip_words = array( 'in', 'the', 'will', 'see', 'and', 'day', 'you', 'after' );
// get words in sentence that aren't to be skipped and count their values
$words = array_count_values( array_diff( explode( ' ', $str ), $skip_words ) );

print_r( $words );