php - sorting an array of words by their relevance to a keyword

array-sorting.php

<?php

    $query = 'ma';
    $names = ['Kevin', 'Michael', 'Joseph', 'Mark', 'Edward', 'Velma', 'William', 'Mary', 'Kimani'];
    // $target = ['Mark', 'Mary', 'Michael', 'Kimani', 'Velma', 'William', 'Edward', 'Joseph', 'Kevin'];
    // $result = ['Mark', 'Mary', 'Kimani', 'Michael', 'Velma', 'William', 'Edward', 'Kevin', 'Joseph'];
    // the slight difference is because the longer words have more irrelevant characters

    function weights($query) { // return weight of letters determined by their order of appearance
        $query = strtolower($query); // eliminate case sensitivity
        $length = strlen($query);
        $weights = []; 
        foreach (str_split($query) as $letter) { // loop through query
            $weights[$letter] = $length*100;
            $length--; // deduct length
        }
        return $weights;
    }
    // return weights($query); // ['m'=>200,'a'=>100];

    function wordWeight($word, $query_weights) { // return weight of letters determined by their order of appearance
        $word = strtolower($word); // eliminate case sensitivity
        $weights = []; // relevance weights 
        $weight = 0; // relevance weight of word 
        $mismatches = 0;
        $letters = str_split($word);
        
        $unique = ''; // track duplicate occurences
        foreach ($letters as $letter) { // loop through query

            if( !strpos($unique, $letter) ){ // if letter has not been tracked

                $unique .= $letter; //track letter

                if(isset($query_weights[$letter]) ){ // if letter exists in query
    
                    // increment weight of word
                    $weight += $query_weights[$letter];
                    $weights[] = $query_weights[$letter];
                    
                    // subtract number of characters before it appears
                    $weight -= strpos($word, $letter);

                }
                else{
                    $mismatches++; // count mismatches
                    $weights[] = '-';
                }
            }
            else{
                $weight -= 1; // rank down
                $weights[] = '-';
            }

        }
        // subtract number of missmatches
        $weight -= $mismatches; 
        
        return $weight;
        // return $weights;
        // return $unique;
    }

    function relevance($words, $query) {
        
        $word_weights = [];
        $query_weights = weights($query);

        foreach ($words as $word) {
            $word_weights[$word] = wordWeight($word, $query_weights);
        }
        return $word_weights;
    }
    
    $weighted = relevance($names, $query);
    // return $weighted;
    
    // multisort: first by values(descending) then by keys (alphabetical)
    array_multisort(array_values($weighted), SORT_DESC, array_keys($weighted), SORT_ASC, $weighted);

    $sorted = array_keys($weighted);
    
    return $sorted;