Subtract two strings in PHP or mySQL to count differences

Question

Is it possible to return the number of characters which differ between two strings?

In my case, I would like to run a check to quantify how much a user's draft has changed vs the database version. With this information, the system can decide weather or not the draft needs to be auto-saved.

For example:

echo string_diff("Hello world", "Hi World");

This should output "5", indicating that characters "ello" & "W" are different.

Is this possible with PHP? How about with mySQL?

have a look at [levenshtein](http://php.net/manual/en/function.levenshtein.php) — Frédéric Clausset, May 27 '13 at 19:27
or as simple as http://php.net/manual/en/function.strcmp.php or substr_compare and co... — Twisted1919, May 27 '13 at 19:28
also levenshtein function with mysql [here](http://stackoverflow.com/questions/4671378/levenshtein-mysql-php) — Frédéric Clausset, May 27 '13 at 19:36

score 3 · Accepted Answer · answered May 27 '13 at 19:35

On the PHP side your options are

similar_text which calculates the percent similarity between two strings
levenshtein - which calculates the edit distance between two strings (the number of key strokes it takes to transform string a into string b)

on mysql you can use this user defined function to calculate the levenshtein distance

Subtract two strings in PHP or mySQL to count differences

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