Since soundex() does not produce optimal results for German language
we have written a function to implement the so called Kölner Phonetik
(Cologne Phonetic).
Please find the code below in the hope it might be useful:
<?php
/**
* A function for retrieving the Kölner Phonetik value of a string
*
* As described at http://de.wikipedia.org/wiki/Kölner_Phonetik
* Based on Hans Joachim Postel: Die Kölner Phonetik.
* Ein Verfahren zur Identifizierung von Personennamen auf der
* Grundlage der Gestaltanalyse.
* in: IBM-Nachrichten, 19. Jahrgang, 1969, S. 925-931
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* @package phonetics
* @version 1.0
* @link http://www.einfachmarke.de
* @license GPL 3.0 <http://www.gnu.org/licenses/>
* @copyright 2008 by einfachmarke.de
* @author Nicolas Zimmer <nicolas dot zimmer at einfachmarke.de>
*/
function cologne_phon($word){
/**
* @param string $word string to be analyzed
* @return string $value represents the Kölner Phonetik value
* @access public
*/
//prepare for processing
$word=strtolower($word);
$substitution=array(
"ä"=>"a",
"ö"=>"o",
"ü"=>"u",
"ß"=>"ss",
"ph"=>"f"
);
foreach ($substitution as $letter=>$substitution) {
$word=str_replace($letter,$substitution,$word);
}
$len=strlen($word);
//Rule for exeptions
$exceptionsLeading=array(
4=>array("ca","ch","ck","cl","co","cq","cu","cx"),
8=>array("dc","ds","dz","tc","ts","tz")
);
$exceptionsFollowing=array("sc","zc","cx","kx","qx");
//Table for coding
$codingTable=array(
0=>array("a","e","i","j","o","u","y"),
1=>array("b","p"),
2=>array("d","t"),
3=>array("f","v","w"),
4=>array("c","g","k","q"),
48=>array("x"),
5=>array("l"),
6=>array("m","n"),
7=>array("r"),
8=>array("c","s","z"),
);
for ($i=0;$i<$len;$i++){
$value[$i]="";
//Exceptions
if ($i==0 AND $word[$i].$word[$i+1]=="cr") $value[$i]=4;
foreach ($exceptionsLeading as $code=>$letters) {
if (in_array($word[$i].$word[$i+1],$letters)){
$value[$i]=$code;
} }
if ($i!=0 AND (in_array($word[$i-1].$word[$i],
$exceptionsFollowing))) {
value[$i]=8;
}
//Normal encoding
if ($value[$i]==""){
foreach ($codingTable as $code=>$letters) {
if (in_array($word[$i],$letters))$value[$i]=$code;
}
}
}
//delete double values
$len=count($value);
for ($i=1;$i<$len;$i++){
if ($value[$i]==$value[$i-1]) $value[$i]="";
}
//delete vocals
for ($i=1;$i>$len;$i++){//omitting first characer code and h
if ($value[$i]==0) $value[$i]="";
}
$value=array_filter($value);
$value=implode("",$value);
return $value;
}
?>