String similarity in PHP: levenshtein like function for long strings

Question

The function levenshtein in PHP works on strings with maximum length 255. What are good alternatives to compute a similarity score of sentences in PHP.

Answer 1

The levenshtein algorithm has a time complexity of O(n*m), where n and m are the lengths of the two input strings. This is pretty expensive and computing such a distance for long strings will take a long time.

For whole sentences, you might want to use a diff algorithm instead, see for example: Highlight the difference between two strings in PHP

Having said this, PHP also provides the similar_text function which has an even worse complexity (O(max(n,m)**3)) but seems to work on longer strings.