CODEWITHSUNDEEP
phpregex
Totumus Maximus
Totumus Maximus

Reputation: 7573

preg_replace doesnt not replace what I want

I have this regex that matches strings that I want to check on validity. However recently I want to use this same regex to replace every character that is not valid to the regex with a character (let's say x).

My regex to match these types of strings is: '#^[\pL\'\’\d][\pL\.\-\ \'\/\,\’\d]*$#iu' Which allows for the first character to be of any language or any digit and some determined special chars. And all the following letters to be slightly the same but slightly more special characters.

This is what I do (nothing special).

    preg_replace($regex, 'x', $string);

Things I tried include trying to negate the regex: '(?![\pL\'\’\d][\pL\.\-\ \'\/\,\’\d]*)' '[^\pL\'\’\d][^\pL\.\-\ \'\/\,\’\d]*'

I've also tried splitting up the string into the firstchar and the rest of the string and split the regex in 2.

$validationRegex1 = '[^\pL\'\’\d]';
$validationRegex2 = '[^\pL\.\-\ \'\/\,\’\d]*';
$fixedStr1 = (string) preg_replace($validationRegex1, 'x', $firstChar)
    . (string) preg_replace($validationRegex2, 'x', $theRest);

But this also did not seemed to work.

I've experimented a bit with this online tool: https://www.functions-online.com/preg_replace.html

Does anyone know what I am overlooking?

Examples of strings and their expected results

'-' should become 'x'.
'Random-morestuff' stays 'Random-morestuff'
'Random%morestuff' should become 'Randomxmorestuff'
'Rândôm' stays 'Rândôm'

Upvotes: 2

Views: 87

Answers (2)

Ryszard Czech
Ryszard Czech

Reputation: 18611

Use

$fixedStr1 = preg_replace('/[\p{L}\'\’\d][\p{L}\.\ \'\/\,\’\d-]*(*SKIP)(*FAIL)|./u', 'x', $input_string);

See regex proof.

Fail matches that match valid symbol words and replace every character appearing in other places.

Upvotes: 1

Jan
Jan

Reputation: 43169

Just an idea but if I got you right, you could use

(?(DEFINE)
    (?<first>[\pL\d'’])
    (?<other>[-\ \pL\d.'/,’])
)
\b(?&first)(?&other)+\b(*SKIP)(*FAIL)|.

This needs to be replaced by x. You do not have to escape everything in a character class, I changed this accordingly.
See a demo on regex101.com.

A bit more explanation: The (?(DEFINE)...) thingy lets you define subroutines that can be used afterwards and is just syntactic sugar in this case (maybe a bit showing off, really). As you have stated that other characters are allowed depending on theirs positions, I just called them first and other. The \b marks a word boundary, that is a boundary between \w (usually [a-zA-Z0-9_]) and \W (not \w). All of these "words" are allowed, so we let the engine "forget" what has been matched with the (*SKIP)(*FAIL) mechanism and match any other character on the right side of the alternation (|). See how (*SKIP)(*FAIL) works here on SO.

Upvotes: 2

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