preg_replace gives back empty string

Question

//Chars to be replaced      
$suchmuster = array();
$suchmuster[0] = 'á';
$suchmuster[1] = 'à';
$suchmuster[2] = 'â';

$suchmuster[3] = 'é';
$suchmuster[4] = 'è';
$suchmuster[5] = 'ê';

$suchmuster[6] = 'í';
$suchmuster[7] = 'ì';
$suchmuster[8] = 'î';

$suchmuster[9] = 'ó';
$suchmuster[10] = 'ò';
$suchmuster[11] = '/ô/';

$suchmuster[12] = 'ú';
$suchmuster[13] = 'ù';
$suchmuster[14] = 'û';

$suchmuster[15] = ' ';
$suchmuster[16] = '.';
$suchmuster[17] = ',';
$suchmuster[18] = '-';
$suchmuster[19] = '_';

//Replaces

$ersetzungen = array();
$ersetzungen[0] = 'a';
$ersetzungen[1] = 'a';
$ersetzungen[2] = 'a';

$ersetzungen[3] = 'e';
$ersetzungen[4] = 'e';
$ersetzungen[5] = 'e';

$ersetzungen[6] = 'i';
$ersetzungen[7] = 'i';
$ersetzungen[8] = 'i';

$ersetzungen[9] = 'o';
$ersetzungen[10] = 'o';
$ersetzungen[11] = 'o';

$ersetzungen[12] = 'u';
$ersetzungen[13] = 'u';
$ersetzungen[14] = 'u';

$ersetzungen[15] = '';
$ersetzungen[16] = '';
$ersetzungen[17] = '';
$ersetzungen[18] = '';
$ersetzungen[19] = '';

$newmessage = preg_replace($suchmuster, $ersetzungen, strtolower($message));

The above code was created to replace some special chars with normal ones but no matter which $nachricht (= $message) I put in, it always gives back an empty string!

Thanks for your help.

EDIT

I Changed it to:

//Chars to be replaced

$suchmuster[0] = '/ /';
$suchmuster[1] = '/./';
$suchmuster[2] = '/,/';
$suchmuster[3] = '/-/';
$suchmuster[4] = '/_/';

//Replaces

$ersetzungen[0] = '';
$ersetzungen[1] = '';
$ersetzungen[2] = '';
$ersetzungen[3] = '';
$ersetzungen[4] = '';

$newmessage = iconv('UTF-8', 'ISO-8859-1//TRANSLIT//IGNORE', strtolower($message));

$newmessage = preg_replace($suchmuster, $ersetzungen, $newmessage);

It still gives back an empty string.

Enable error_reporting. Except /ô/ none of your $suchmusters are valid regexps. If the charset is Latin-1, consider str_replace or strtr instead. — mario
– mario, Commented Dec 7, 2013 at 13:40
You know you can assign an array like this: $suchmuster = array('á', 'à', 'â', /* etc. */); — EricSchaefer
– EricSchaefer, Commented Dec 7, 2013 at 13:42
If you want just get rid of the diacritics, you can also use iconv like iconv('UTF-8', 'US-ASCII//TRANSLIT', $string). — Marcel Korpel
– Marcel Korpel, Commented Dec 7, 2013 at 13:44
Thank you. error_reporting doesn't return anything. It doesn't work even if I put every char to be replaced in "/ /" — Nico Enking
– Nico Enking, Commented Dec 7, 2013 at 13:44
Marc Korpel, thank you I found this a few seconds ago. I also don't want any special chars like "-" or "_" for example. — Nico Enking
– Nico Enking, Commented Dec 7, 2013 at 13:45

HamZa · Accepted Answer · 2013-12-08 11:33:13Z

1

Instead of using several patterns, you can also combine the pattern to:

$nachrichtneu = preg_replace('/[,.\s_-]/', '', $nachrichtneu);

And strtolower will not convert Á and the like to á. First do the iconv conversion, then the strtolower.

edited Dec 8, 2013 at 11:33

HamZa

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answered Dec 7, 2013 at 14:01

Marcel Korpel

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4 Comments

Marcel Korpel Over a year ago

@NicoEnking And the reason you got back an empty string is explained by Kaii in their answer.

Marcel Korpel Over a year ago

@HamZa Isn't escaping the dot necessary to prevent it matching every character?

HamZa Over a year ago

@MarcelKorpel In a character class, the dot loses it's meaning, so it becomes a literal dot characters Which means it's redundant to escape it. See this demo. The same goes for a hyphen at the begin or end of a character class. See this demo.

Marcel Korpel Over a year ago

@HamZa I just tested this myself, too. Thanks for the links to regex101.com, I didn't know that site and it looks very useful.

Kaii · Accepted Answer · 2013-12-08 14:33:56Z

1

Regarding your updated question:

Regular expressions use special control characters. In your case it is /./ which causes your result to be empty. . means "any character" in regex, so you are replacing each and every character with nothing.

use preg_quote() to escape special characters in regular expressions. Example: $xy = '/' . preg_quote('.') . '/';

But you can do this much simpler without using regular expressions, like:

$replaces = array(
    '.' => '',
    ',' => '',
    // ...
);
$message = str_replace(array_keys($replaces), array_values($replaces), $message);

edited Dec 8, 2013 at 14:33

answered Dec 7, 2013 at 14:03

Kaii

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Comments

Ulrich Horus · Accepted Answer · 2013-12-07 13:47:07Z

0

change your code through

$suchmuster = array();
$suchmuster[0] = "/á/";
$suchmuster[1] = "/à/";

...

answered Dec 7, 2013 at 13:47

Ulrich Horus

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1 Comment

Nico Enking Over a year ago

I have updated my code but it still doesnt work (See my edit above)

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