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Just trying to use Craft's Twig replace filter to remove number prefixes from the beginning of User Groups names and I have had to double escape the character classes etc to get it to work. I tried this...

{{ group.name|replace('/^\d+\.\s/','') }}{% if not loop.last %}, {% endif %}

and it didn't work so for some reason I tried this...

{{ group.name|replace('/^\\d+\\.\\s/','') }}{% if not loop.last %}, {% endif %}

...and it worked. Is there a sensible explanation for this as Regular Expressions are like Voodoo?!

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  • Meant to say the docs show only single backslashes hence the confusion...
    – Neal Hulme
    Commented Oct 21, 2014 at 19:23
  • Neal, I came across the same mystery using Twig's matches operator, which was also wrong in Sensiolabs' docs.
    – carlcs
    Commented Oct 22, 2014 at 7:38

1 Answer 1

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Twig auto-escapes the \ character so by the time it makes it to the Craft replace filter PHP code, the regex string looks like /^d+.s/.

By double escaping it, you're forcing the correct regex to make it through /^\d+\.\s/.

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  • Glad there is a sensible explanation... is this documented anywhere for future reference?
    – Neal Hulme
    Commented Oct 21, 2014 at 20:12
  • Is now! buildwithcraft.com/docs/templating/filters#replace
    – Brad Bell ♦
    Commented Oct 21, 2014 at 20:29
  • Awesome, thanks Brad!
    – Neal Hulme
    Commented Oct 21, 2014 at 20:46
  • This is not a Craft-CMS related comment, but I want to say I could only use the matches operator in TWIG to validate a string against a regular expression when I used double-escaping in my regexp.
    – Marcos Buarque
    Commented May 16, 2022 at 18:20

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