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similar_text — Calculates the similarity of two strings.


int similar_text(string_one, string_two[, $percent]);
string string_one: First string to be compared
string string_two: Second string to be compared
variable $percent (optional): Variable to store the percentage similarity of the strings


Number of characters that match between the two strings


similar_text() calculates the similarity of two strings. The function returns the number of unique characters that appear in both strings. The function can store the percentage similarity of the strings in the optional $percent parameter.


PHP 3.0.7, PHP 4+ since 4.0b2

See also

Faster (but less accurate) method to analyze the similarity of two strings:


To generate a phonetic-based key for a string:



Paper from which the similar_text() algorithm is derived:

An Extension of Decision Trees (Jonathan J. Oliver)


Example 1218. A cheesy example

$term = 'cheese';
foreach(array('gouda', 'gruyere', 'cheddar') as $match) {
   echo similar_text($term, $match, $percent),
      " characters from '$term' were contained in '$match'.\n",
      "Overall, '$term' is a ", round($percent),
      "% match for '$match'\n\n";

0 characters from 'cheese' were contained in 'gouda'.
Overall, 'cheese' is a 0% match for 'gouda'

2 characters from 'cheese' were contained in 'gruyere'.
Overall, 'cheese' is a 31% match for 'gruyere'

3 characters from 'cheese' were contained in 'cheddar'.
Overall, 'cheese' is a 46% match for 'cheddar'

PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at The authors of this book have elected not to choose any options under the OPL. This online book was obtained from and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.

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