similar_text 


string apg

CALCULATE the similarity between two strings.





Swapping the $first and $second may yield a different result.

This function 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.



<?php

int similar_text ( str $first , str $second [, float &$percent ] ) 


where,

$first = The first STRING

$second = The second STRING

&$percent = The percentage of similarity
                    ( PASSED be reference )

?> 

$first


The first STRING.



$second


The second STRING.



&$percent


The similarity percentage between $first and $second.



  1 EXERCISE   

<?php

$first01 = 'Window';

$second01 = 'Widow';

// setlocale(LC_ALL, 'pt-BR', 'pt_BR');

$sim01a = similar_text($first01, $second01, $percent01);

echo '(' . $sim01a . ') The similarity between<br>' . 
                     $first01 . '<br>and<br>'. $second01 . '<br>is<br>' . 
                                              $percent01 . '%<br><br>';

$sim01b = similar_text($second01, $first01, $percent01);

echo '(' . $sim01a . ') The similarity between<br>' . 
                     $second01 . '<br>and<br>'. $first01 . '<br>is<br>' . 
                                                   $percent01 . '%<br><br>';

?> 

 RESULT   

(5) The similarity between
Window
and
Widow
is
90.909090909091%

(5) The similarity between
Widow
and
Window
is
90.909090909091%

  2 EXERCISE   

<?php

$first02 = 'Levenshtein';

$second02 = 'Soundex';

$sim02a = similar_text($first02, $second02, $percent02); 

echo '(' . $sim02a . ') The similarity between<br>' . 
                             $first02 . '<br>and<br>'. 
                             $second02 . '<br>is<br>' . 
                             $percent02 . '%<br><br>'; 

$sim02b = similar_text($second02, $first02, $percent02); 

echo '(' . $sim02b . ') The similarity between<br>' . 
                                      $second02 . '<br>and<br>'. 
                                      $first02 . '<br>is<br>' . 
                                      $percent02 . '%<br><br>'; 

?> 

 RESULT   

(1) The similarity between
Levenshtein
and
Soundex
is
11.111111111111%

(2) The similarity between
Soundex
and
Levenshtein
is
22.222222222222%

  3 EXERCISE   

<?php

function smlartxt($parA, $parB)
{
    $smlr = similar_text($parA, $parB, $perc);
    echo "[ $smlr ] ( $parA, $parB ) = $perc% <br><br>";
}

smlartxt("abcdefgh", "efg");

smlartxt("abcdefgh", "mno");

smlartxt("abcdefghcc", "c");

smlartxt("abcdefghabcdef", "zzzzabcdefggg");

smlartxt("abcdef", "abcdef");
?>