levenshtein
(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)
levenshtein — Calculate Levenshtein distance between two strings
Description
string
$string1,string
$string2,int
$insertion_cost = 1,int
$replacement_cost = 1,int
$deletion_cost = 1): int
The Levenshtein distance is defined as the minimal number of
characters you have to replace, insert or delete to transform
string1 into string2.
The complexity of the algorithm is O(m*n),
where n and m are the
length of string1 and
string2 (rather good when compared to
similar_text(), which is O(max(n,m)**3),
but still expensive).
If insertion_cost, replacement_cost
and/or deletion_cost are unequal to 1,
the algorithm adapts to choose the cheapest transforms.
E.g. if $insertion_cost + $deletion_cost < $replacement_cost,
no replacements will be done, but rather inserts and deletions instead.
Parameters
-
string1 -
One of the strings being evaluated for Levenshtein distance.
-
string2 -
One of the strings being evaluated for Levenshtein distance.
-
insertion_cost -
Defines the cost of insertion.
-
replacement_cost -
Defines the cost of replacement.
-
deletion_cost -
Defines the cost of deletion.
Return Values
This function returns the Levenshtein-Distance between the two argument strings or -1, if one of the argument strings is longer than the limit of 255 characters.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | Prior to this version, levenshtein() had to be called with either two or five arguments. |
Examples
Example #1 levenshtein() example
<?php
// input misspelled word
$input = 'carrrot';
// array of words to check against
$words = array('apple','pineapple','banana','orange',
'radish','carrot','pea','bean','potato');
// 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";
}
?>
The above example will output:
Input word: carrrot Did you mean: carrot?
See Also
- soundex() - Calculate the soundex key of a string
- similar_text() - Calculate the similarity between two strings
- metaphone() - Calculate the metaphone key of a string
