CODEWITHSUNDEEP
phpregexregex-negation
Frantisek
Frantisek

Reputation: 7693

Backward negativity in regex (php)

I'm using regex with PHP's preg_replace when processing user input to make hyperlinks come to life using this piece of code:

preg_replace(
   '!(((f|ht)tp://)[-a-zA-Zа-яА-Я()0-9@:%_+.~#?&;//=]+)!i',
   '<a class="external" href="$1">$1</a>',
   $text
);

What I need to do, however, is to ignore all links encased in {{ }}, so for example, this input should be processed by regex:

http://www.example.com/

This input should be ignored:

{{http://www.example.com/}}

How can I change my regex pattern to work as expected?

Upvotes: 0

Views: 90

Answers (1)

fge
fge

Reputation: 121720

Surround your regex with a negative lookbehind ((?<!...)) and a negative lookahead ((?!...)):

'/(?<!\{\{)(((f|ht)tp:\/\/)[-a-zа-я()0-9@:%_+.~#?&;\/=]+)(?!\}\})/i'

Alternatively, just go through the text word by word, and try and see if a word is a valid URL using a URL parsing library (you cannot have a space in a URL); and replace only in this case.

Upvotes: 3

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