How to sort an array by similarity in relation to an inputted word.

Question

I have on PHP array, for example:

$arr = array(\"hello\", \"try\", \"hel\", \"hey hello\");

Now I want to do rearrange of the array which w

Answer 1

While @yceruto's answer is correct and informative, I would like to extend additional insights and demonstrate more modern implementation syntax.

• The three-way comparison operator (aka "spaceship operator") <=> from PHP7+
• Arrow function syntax to allow extra variables into the custom function scope from PHP7.4+.

First about the generated scores from respective functions...

1. levenshtein() and similar_text() ARE case-sensitive so an uppercase H is just as much a mismatch as the number 6 when compared to h.
2. levenshtein() and similar_text() ARE NOT multi-byte aware so an accented character like ê will not only be deemed a mismatch for e, it will potentially receive a heavier penalty based on each individual byte being a mismatch.

If you want to make case-insensitive comparisons, you can simply convert both strings to uppercase/lowercase before executing.

If your application requires multi-byte support, you should search for existing repositories that provide this functionality.

Additional techniques for those willing to research more deeply include metaphone() and soundex(), but I will not delve into these topics in this answer.

Scores:

Test vs "hello" |  levenshtein   |  similar_text  |   similar_text's percent   |
----------------+----------------+----------------+----------------------------|
H3||0           |       5        |      0         |       0                    |
Hallo           |       2        |      3         |      60                    |
aloha           |       5        |      2         |      40                    |
h               |       4        |      1         |      33.333333333333       |
hallo           |       1        |      4         |      80                    |
hallå           |       3        |      3         |      54.545454545455       |
hel             |       2        |      3         |      75                    |
helicopter      |       6        |      4         |      53.333333333333       |
hellacious      |       5        |      5         |      66.666666666667       |
hello           |       0        |      5         |     100                    |
hello y'all     |       6        |      5         |      62.5                  |
hello yall      |       5        |      5         |      66.666666666667       |
helów           |       3        |      3         |      54.545454545455       |
hey hello       |       4        |      5         |      71.428571428571       |
hola            |       3        |      2         |      44.444444444444       |
hêllo           |       2        |      4         |      72.727272727273       |
mellow yellow   |       9        |      4         |      44.444444444444       |
try             |       5        |      0         |       0                    |

---

Sort by levenshtein() PHP7+ (Demo)

usort($testStrings, function($a, $b) use ($needle) {
    return levenshtein($needle, $a) <=> levenshtein($needle, $b);
});

Sort by levenshtein() PHP7.4+ (Demo)

usort($testStrings, fn($a, $b) => levenshtein($needle, $a) <=> levenshtein($needle, $b));

---

Notice that $a and $b have changed sides of the <=> evaluation for DESC ordering. **Notice that hello is not assured to be positioned as first element

Sort by similar_text() PHP7+ (Demo)

usort($testStrings, function($a, $b) use ($needle) {
    return similar_text($needle, $b) <=> similar_text($needle, $a);
});

Sort by similar_text() PHP7.4+ (Demo)

usort($testStrings, fn($a, $b) => similar_text($needle, $b) <=> similar_text($needle, $a));

---

Notice the difference in scoring of hallå and helicopter via similar_text()'s return value versus similar_text()'s percent value.

Sort by similar_text()'s percent PHP7+ (Demo)

usort($testStrings, function($a, $b) use ($needle) {
    similar_text($needle, $a, $percentA);
    similar_text($needle, $b, $percentB);
    return $percentB <=> $percentA;
});

Sort by similar_text()'s percent PHP7.4+ (Demo)

usort($testStrings, fn($a, $b) => 
    [is_int(similar_text($needle, $b, $percentB)), $percentB]
    <=>
    [is_int(similar_text($needle, $a, $percentA)), $percentA]
);

Notice that I am neutralizing the unwanted return value of similar_text() by converting its return value to true, then using the generated percent value -- this allows the generation of the percent value without returning too soon since arrow function syntax does not permit multi-line execution.

---

Sort by levenshtein() then break ties with similar_text() PHP7+ (Demo)

usort($testStrings, function($a, $b) use ($needle) {
    return [levenshtein($needle, $a), similar_text($needle, $b)]
           <=>
           [levenshtein($needle, $b), similar_text($needle, $a)];
});

Sort by levenshtein() then break ties with similar_text()'s percent PHP7.4+ (Demo)

usort($testStrings, fn($a, $b) =>
    [levenshtein($needle, $a), similar_text($needle, $b)]
    <=>
    [levenshtein($needle, $b), similar_text($needle, $a)]
);

Personally, I never use anything but levenshtein() in my projects because it consistently delivers the results that I'm looking for.

Answer 2

if you want to sort your array, you can do this:

$arr = array("hello", "try", "hel", "hey hello");
$search = "hey"; //your search var

for($i=0; $i<count($arr); $i++) {
   $temp_arr[$i] = levenshtein($search, $arr[$i]);
}
asort($temp_arr);
foreach($temp_arr as $k => $v) {
    $sorted_arr[] = $arr[$k];
}

$sorted_arr should then be in descending order starting with the closest word to your search term.

Answer 3

You can use levenshtein function

<?php
// input misspelled word
$input = 'helllo';

// array of words to check against
$words  = array('hello' 'try', 'hel', 'hey hello');

// no shortest distance found, yet
$shortest = -1;

// loop through words to find the closest
foreach ($words as $word) {

    // calculate the distance between the input word,
    // and the current word
    $lev = levenshtein($input, $word);

    // check for an exact match
    if ($lev == 0) {

        // closest word is this one (exact match)
        $closest = $word;
        $shortest = 0;

        // break out of the loop; we've found an exact match
        break;
    }

    // if this distance is less than the next found shortest
    // distance, OR if a next shortest word has not yet been found
    if ($lev <= $shortest || $shortest < 0) {
        // set the closest match, and shortest distance
        $closest  = $word;
        $shortest = $lev;
    }
}

echo "Input word: $input\n";
if ($shortest == 0) {
    echo "Exact match found: $closest\n";
} else {
    echo "Did you mean: $closest?\n";
}

?>

Answer 4

This is a quick solution by using http://php.net/manual/en/function.similar-text.php:

This calculates the similarity between two strings as described in Programming Classics: Implementing the World's Best Algorithms by Oliver (ISBN 0-131-00413-1). Note that this implementation does not use a stack as in Oliver's pseudo code, but recursive calls which may or may not speed up the whole process. Note also that the complexity of this algorithm is O(N**3) where N is the length of the longest string.

$userInput = 'Bradley123';

$list = array('Bob', 'Brad', 'Britney');

usort($list, function ($a, $b) use ($userInput) {
    similar_text($userInput, $a, $percentA);
    similar_text($userInput, $b, $percentB);

    return $percentA === $percentB ? 0 : ($percentA > $percentB ? -1 : 1);
});

var_dump($list); //output: array("Brad", "Britney", "Bob");

---

Or using http://php.net/manual/en/function.levenshtein.php:

The Levenshtein distance is defined as the minimal number of characters you have to replace, insert or delete to transform str1 into str2. The complexity of the algorithm is O(m*n), where n and m are the length of str1 and str2 (rather good when compared to similar_text(), which is O(max(n,m)**3), but still expensive).

$userInput = 'Bradley123';

$list = array('Bob', 'Brad', 'Britney');

usort($list, function ($a, $b) use ($userInput) {
    $levA = levenshtein($userInput, $a);
    $levB = levenshtein($userInput, $b);

    return $levA === $levB ? 0 : ($levA > $levB ? 1 : -1);
});

var_dump($list); //output: array("Britney", "Brad", "Bob");

Answer 5

Another way is to use similar_text function which returns result in percents. See more http://www.php.net/manual/en/function.similar-text.php .