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. Test similar_text online.
int similar_text ( string $first , string $second [, float &$percent ] )
PHP Documentation by the PHP Documentation Group
(PHP 4, PHP 5, PHP 7)
similar_text — Calculate the similarity between two strings
$first
, string $second
[, float &$percent
] ) : int
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.
first
The first string.
second
The second string.
Note:
Swapping the
first
andsecond
may yield a different result; see the example below.
percent
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.
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 #1 similar_text() argument swapping example
This example shows that swapping the first
and
second
argument may yield different results.
<?php
$sim = similar_text('bafoobar', 'barfoo', $perc);
echo "similarity: $sim ($perc %)\n";
$sim = similar_text('barfoo', 'bafoobar', $perc);
echo "similarity: $sim ($perc %)\n";
The above example will output something similar to:
similarity: 5 (71.428571428571 %) similarity: 3 (42.857142857143 %)
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