[doc-en] master: Fix PCRE pattern syntax docs: \R, \x{...}/\N{U+...} escapes, unicode section, lookahead terminology (#5892)

Author: Louis-Arnaud (lacatoire) Committer: GitHub (web-flow) Pusher: lacatoire Date: 2026-10-24T08:06:17+02:00 Commit: https://github.com/php/doc-en/commit/75ed9b0163e3e0563e82fdb98ef1cc9008c794a9 Raw diff: https://github.com/php/doc-en/commit/75ed9b0163e3e0563e82fdb98ef1cc9008c794a9.diff Fix PCRE pattern syntax docs: \R, \x{...}/\N{U+...} escapes, unicode section, lookahead terminology (#5892) * Fix PCRE pattern syntax docs: \R, \x{...}/\N{U+...} escapes, unicode section, lookahead terminology - Correct the claim that \d/\w never use Unicode properties in PCRE: since PHP 5.4.0 the u modifier implies PCRE_UCP. - Document the two \R behaviors (default Unicode line break sequence vs (*BSR_ANYCRLF)). - Add \x{hhhh} and \N{U+hhhh} Unicode escape entries. - Make "lookahead"/"lookbehind" appear as single searchable terms in the assertions section intro. Fixes: #2831, #4493, #5404, #4438 * Fix docbook-cs violations: para -> simpara for inline-only content * Clarify \N{U+hhhh}/\x{hhhh} equivalence is scoped to UTF-8 mode Changed paths: M reference/pcre/pattern.syntax.xml Diff: diff --git a/reference/pcre/pattern.syntax.xml b/reference/pcre/pattern.syntax.xml index 473459a7f938..6d13bbaeaba3 100644 --- a/reference/pcre/pattern.syntax.xml +++ b/reference/pcre/pattern.syntax.xml @@ -320,7 +320,15 @@ <varlistentry> <term><emphasis>\R</emphasis></term> <listitem> - <simpara>line break: matches \n, \r and \r\n</simpara> + <simpara> + line break. By default, <literal>\R</literal> matches any Unicode + newline sequence: in 8-bit non-UTF-8 mode this is equivalent to + <literal>(?&gt;\r\n|\n|\x0b|\f|\r|\x85)</literal>; in UTF-8 mode, two + further characters, U+2028 and U+2029, are added. If the pattern + contains the <literal>(*BSR_ANYCRLF)</literal> special sequence, + <literal>\R</literal> matches only <literal>\r\n</literal>, + <literal>\r</literal> and <literal>\n</literal>. + </simpara> </listitem> </varlistentry> <varlistentry> @@ -337,6 +345,26 @@ </simpara> </listitem> </varlistentry> + <varlistentry> + <term><emphasis>\x{hhhh}</emphasis></term> + <listitem> + <simpara> + in <emphasis>UTF-8 mode</emphasis>, the Unicode character whose code + point is the given hexadecimal number + </simpara> + </listitem> + </varlistentry> + <varlistentry> + <term><emphasis>\N{U+hhhh}</emphasis></term> + <listitem> + <simpara> + in <emphasis>UTF-8 mode</emphasis>, the Unicode character whose code + point is the given hexadecimal number, equivalent in that mode to + <literal>\x{hhhh}</literal>; unlike <literal>\x{hhhh}</literal>, this + syntax is not recognized outside UTF-8 mode + </simpara> + </listitem> + </varlistentry> <varlistentry> <term><emphasis>\ddd</emphasis></term> <listitem> @@ -1095,13 +1123,19 @@ <xref linkend="regexp.reference.onlyonce"/>). Characters with the "mark" property are typically accents that affect the preceding character. </simpara> - <para> + <simpara> Matching characters by Unicode property is not fast, because PCRE has to search a structure that contains data for over fifteen thousand - characters. That is why the traditional escape sequences such as - <literal>\d</literal> and <literal>\w</literal> do not use Unicode properties - in PCRE. - </para> + characters. Since PHP 5.4.0, the generic character type escape sequences + <literal>\d</literal>, <literal>\s</literal> and <literal>\w</literal> (and + their upper case counterparts) use Unicode properties when the + <link linkend="reference.pcre.pattern.modifiers">PCRE_UTF8</link> + (<literal>u</literal>) modifier is set, so that, for example, + <literal>\d</literal> also matches non-ASCII decimal digits. Before PHP + 5.4.0, these escape sequences did not use Unicode properties, for + efficiency reasons, unless <literal>(*UCP)</literal> was explicitly + added to the pattern. + </simpara> </section> <section xml:id="regexp.reference.anchors"> @@ -1879,15 +1913,16 @@ <section xml:id="regexp.reference.assertions"> <title>Assertions</title> - <para> + <simpara> An assertion is a test on the characters following or preceding the current matching point that does not actually consume any characters. The simple assertions coded as \b, \B, \A, \Z, \z, ^ and $ are described in <link linkend="regexp.reference.escape">escape sequences</link>. More complicated assertions are coded as subpatterns. There are two - kinds: those that <emphasis>look ahead</emphasis> of the current position in the - subject string, and those that <emphasis>look behind</emphasis> it. - </para> + kinds: <emphasis>lookahead</emphasis> assertions, which look ahead of the + current position in the subject string, and + <emphasis>lookbehind</emphasis> assertions, which look behind it. + </simpara> <para> An assertion subpattern is matched in the normal way, except that it does not cause the current matching position to be