similar_text()
similar_text() — Calculate the similarity between two strings.
Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.
What it does
This calculates the similarity between two strings as described in Programming Classics: Implementing the World's Best Algorithms by Oliver (ISBN 0-131-00413-1). Note that this implementation does not use a stack as in Oliver's pseudo code, but recursive calls which may or may not speed up the whole process. Note also that the complexity of this algorithm is O(N**3) where N is the length of the longest string.
Signature
similar_text(string $string1, string $string2, float &$percent = null): int
Parameters
| Parameter | Type | What it takes |
|---|---|---|
| $string1 | string | The first string. |
| $string2 | string | The second string. |
| &$percent | float | By passing a reference as third argument, similar_text() will calculate the similarity in percent, by dividing the result of similar_text() by the average of the lengths of the given strings times 100. |
Return value
Returns the number of matching chars in both strings. The number of matching characters is calculated by finding the longest first common substring, and then doing this for the prefixes and the suffixes, recursively. The lengths of all found common substrings are added.
Example
A runnable snippet:
$sim = similar_text('bafoobar', 'barfoo', $perc); echo "similarity: $sim ($perc %)\n"; $sim = similar_text('barfoo', 'bafoobar', $perc); echo "similarity: $sim ($perc %)\n";
Output:
similarity: 5 (71.428571428571 %) similarity: 3 (42.857142857143 %)
See also
levenshtein(), metaphone(), soundex()
All PHP 8.5 built-in functions
Reference card built from the PHP manual page similar_text() (PHP documentation, CC BY 3.0). The page is generated from the manual, so the wording of the parameter and return value text follows php.net.