[DOC-CVS] [doc-en] master: Clarify that PCRE delimiters must be ASCII characters (#4817) (#5223)

Author: Louis-Arnaud (lacatoire)
Committer: GitHub (web-flow)
Pusher: lacatoire
Date: 2026-08-26T10:12:59+02:00

Commit: https://github.com/php/doc-en/commit/61d512bfd7098a177b6490e0b478c72ed6fb90d6
Raw diff: https://github.com/php/doc-en/commit/61d512bfd7098a177b6490e0b478c72ed6fb90d6.diff

Clarify that PCRE delimiters must be ASCII characters (#4817) (#5223)

Multi-byte UTF-8 characters cannot be used as delimiters since they are
processed at the byte level.

Changed paths:
  M  reference/pcre/pattern.syntax.xml


Diff:

diff --git a/reference/pcre/pattern.syntax.xml b/reference/pcre/pattern.syntax.xml
index c87e73c4804e..2089643135d0 100644
--- a/reference/pcre/pattern.syntax.xml
+++ b/reference/pcre/pattern.syntax.xml
@@ -28,12 +28,20 @@
  </section>
  <section xml:id="regexp.reference.delimiters">
   <title>Delimiters</title>
-  <para>
+  <simpara>
    When using the PCRE functions, it is required that the pattern is enclosed
    by <emphasis>delimiters</emphasis>. A delimiter can be any non-alphanumeric,
-   non-backslash, non-whitespace character.
+   non-backslash, non-whitespace single-byte character.
    Leading whitespace before a valid delimiter is silently ignored.
-  </para>
+  </simpara>
+  <note>
+   <simpara>
+    Multi-byte characters (such as UTF-8 encoded characters like <literal>§</literal>)
+    cannot be used as delimiters. PHP reads exactly one byte as the delimiter;
+    using a multi-byte character would cause the remaining bytes to be
+    misinterpreted as unknown pattern modifiers.
+   </simpara>
+  </note>
   <para>
    Often used delimiters are forward slashes (<literal>/</literal>), hash
    signs (<literal>#</literal>) and tildes (<literal>~</literal>). The