levenshtein

The Levenshtein distance is defined as the minimal number of characters you have to replace, insert or delete to transform $str1 into $str2.

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.