php / php/doc-en

PCRE lookahead

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Description

I know there is a PCRE syntax for looking ahead but not including a trailing match pattern, but it is impossible to find in the Manual. Searching for "lookahead" returns nothing useful. The PCRE syntax page (https://www.php.net/manual/en/reference.pcre.pattern.syntax.php) doesn't describe the syntax. It lists links for:

Introduction
Delimiters
Meta-characters
Escape sequences
Unicode character properties
Anchors
Dot
Character classes
Alternation
Internal option setting
Subpatterns
Repetition
Back references
Assertions
Once-only subpatterns
Conditional subpatterns
Comments
Recursive patterns
Performance

So you have to know about the particular syntax in order to choose the correct link.

Can this please be fixed? I want to use lookahead.

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the PCRE pattern syntax page and its linked Assertions page, then check how the manual exposes lookahead syntax. Done means the documentation makes lookahead discoverable when searching or browsing the syntax references and describes the relevant syntax.

Written by the indexing model from the issue text.

Assessment

Tech stack
php
Domain
documentation
Issue type
Documentation
Difficulty
1/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
45/100

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