(PHP 4 >= 4.0.1, PHP 5)
levenshtein — Calculate Levenshtein distance between two strings
$str1
, string $str2
)$str1
, string $str2
, int $cost_ins
, int $cost_rep
, int $cost_del
)
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).
In its simplest form the function will take only the two
strings as parameter and will calculate just the number of
insert, replace and delete operations needed to transform
str1 into str2.
A second variant will take three additional parameters that define the cost of insert, replace and delete operations. This is more general and adaptive than variant one, but not as efficient.
str1
One of the strings being evaluated for Levenshtein distance.
str2
One of the strings being evaluated for Levenshtein distance.
cost_ins
Defines the cost of insertion.
cost_rep
Defines the cost of replacement.
cost_del
Defines the cost of deletion.
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.
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?