Some characters in the string cannot be replaced

Question

I am trying to change this string

Test - GGA ökologie Geschäftsführer.PDF

into this:

test_-_gga_oekologie_geschaaeftsfuuehrer.pdf

This is what I have tried:

$characters = array('ä', 'ö', 'ü', 'Ä', 'Ö', 'Ü', ' ');
$converted_characters = array('ae', 'oe', 'ue', 'AE', 'OE', 'UE', '_');
$string = 'Test - GGA ökologie Geschäftsführer.PDF';

echo strtolower(str_replace($characters, $converted_characters , $string));

The code above returns: test_-_gga_ökologie_geschäftsführer.pdf

As you see the string still contains the characters ö and ä.

What is wrong with my code?

Answer 1

They are not the same unicode character. If you copy and paste the ö character from your string and paste it in the array it works as intended.

Answer 2

With regex

$characters = array('/ä/u', '/ö/u', '/ü/u', '/Ä/u', '/Ö/u', '/Ü/u', '/ /' );
$converted_characters = array('ae', 'oe', 'ue', 'AE', 'OE', 'UE', '_');  
$string = 'Test - GGA ökologie Geschäftsführer.PDF';

echo strtolower(preg_replace($characters, $converted_characters , $string));