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similar_text (PHP 3 >= 3.0.7, PHP 4, PHP 5) similar_text --
Calculate the similarity between two strings
Descriptionint similar_text ( string first, string second [, float &percent] )
This calculates the similarity between two strings as described
in Oliver [1993]. 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.
By passing a reference as third argument,
similar_text() will calculate the similarity
in percent for you. It returns the number of matching chars in
both strings.
See also levenshtein(), and soundex().
User Contributed Noteslouis #at# mulliemedia.com
07-Jun-2004 02:01
Note that this function will calculate the percentage blindly, without regard to the LENGHT of the string.
This may become important if you try to print similar names to SMALL strings :
e.g.
I want to print out the value if it is 90 percent similar to the other one : the value is HE, the correct value is HEC
The similar_text() function will return approximately 66.7 %, and it will not print it because it is smaller than 90 %, although almost all of the string was matched.
hate at spam dot com dot BR
10-May-2004 06:21
In PHP4+, you don't need to pass the percent variable as reference..
Instead, use this way:
<?
similar_text($string1, $string2, $p);
echo "Percent: $p%";
?>
In PHP5, you'll get a ugly warning message when passing this variable as reference.. But it's configurable in php.ini (allow_call_time_pass_reference = Off)
That's it... Another great function! :)
julius at infoguiden dot no
06-Feb-2003 03:46
If you have reserved names in a database that you don't want others to use, i find this to work pretty good.
I added strtoupper to the variables to validate typing only. Taking case into consideration will decrease similarity.
$query = mysql_query("select * from $table") or die("Query failed");
while ($row = mysql_fetch_array($query)) {
similar_text(strtoupper($_POST['name']), strtoupper($row['reserved']), $similarity_pst);
if (number_format($similarity_pst, 0) > 90){
$too_similar = $row['reserved'];
print "The name you entered is too similar the reserved name "".$row['reserved'].""";
break;
}
}
georgesk at hotmail dot com
09-Mar-2002 05:14
Well, as mentioned above the speed is O(N^3), i've done a longest common subsequence way that is O(m.n) where m and n are the length of str1 and str2, the result is a percentage and it seems to be exactly the same as similar_text percentage but with better performance... here's the 3 functions i'm using..
function LCS_Length($s1, $s2)
{
$m = strlen($s1);
$n = strlen($s2);
//this table will be used to compute the LCS-Length, only 128 chars per string are considered
$LCS_Length_Table = array(array(128),array(128));
//reset the 2 cols in the table
for($i=1; $i < $m; $i++) $LCS_Length_Table[$i][0]=0;
for($j=0; $j < $n; $j++) $LCS_Length_Table[0][$j]=0;
for ($i=1; $i <= $m; $i++) {
for ($j=1; $j <= $n; $j++) {
if ($s1[$i-1]==$s2[$j-1])
$LCS_Length_Table[$i][$j] = $LCS_Length_Table[$i-1][$j-1] + 1;
else if ($LCS_Length_Table[$i-1][$j] >= $LCS_Length_Table[$i][$j-1])
$LCS_Length_Table[$i][$j] = $LCS_Length_Table[$i-1][$j];
else
$LCS_Length_Table[$i][$j] = $LCS_Length_Table[$i][$j-1];
}
}
return $LCS_Length_Table[$m][$n];
}
function str_lcsfix($s)
{
$s = str_replace(" ","",$s);
$s = ereg_replace("[
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