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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.grapheme-substr" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>grapheme_substr</refname>
<refpurpose>Return part of a string</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<para>&style.procedural;</para>
<methodsynopsis>
<type class="union"><type>string</type><type>false</type></type><methodname>grapheme_substr</methodname>
<methodparam><type>string</type><parameter>string</parameter></methodparam>
<methodparam><type>int</type><parameter>offset</parameter></methodparam>
<methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>length</parameter><initializer>&null;</initializer></methodparam>
</methodsynopsis>
<para>
Return part of a string
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>string</parameter></term>
<listitem>
<para>
The input string. Must be valid UTF-8.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>offset</parameter></term>
<listitem>
<para>
Start position in default grapheme units.
If <parameter>offset</parameter> is non-negative, the returned string will start at the
<parameter>offset</parameter>'th position in <parameter>string</parameter>, counting from zero. If <parameter>offset</parameter> is negative,
the returned string will start at the <parameter>offset</parameter>'th grapheme unit from the
end of string.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>length</parameter></term>
<listitem>
<para>
Length in grapheme units.
If <parameter>length</parameter> is given and is positive, the string returned will contain
at most <parameter>length</parameter> grapheme units beginning from <parameter>offset</parameter> (depending on the
length of string). If <parameter>length</parameter> is given and is negative, then
that many grapheme units will be omitted from the end of string (after the
start position has been calculated when <parameter>offset</parameter> is negative). If <parameter>offset</parameter>
denotes a position beyond this truncation, an empty string will be returned.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns the extracted part of <parameter>string</parameter>, &return.falseforfailure;.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>8.0.0</entry>
<entry>
The function now consistently clamps out-of-bounds offsets to the string boundary.
Previously, &false; was returned instead of the empty string in some cases.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<example>
<title><function>grapheme_substr</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$char_a_ring_nfd = "a\xCC\x8A"; // 'LATIN SMALL LETTER A WITH RING ABOVE' (U+00E5) normalization form "D"
$char_o_diaeresis_nfd = "o\xCC\x88"; // 'LATIN SMALL LETTER O WITH DIAERESIS' (U+00F6) normalization form "D"
print urlencode(grapheme_substr( "ao" . $char_a_ring_nfd . "bc" . $char_o_diaeresis_nfd . "O", 2, -1 ));
?>
]]>
</programlisting>
</example>
&example.outputs;
<screen>
<![CDATA[
a%CC%8Abco%CC%88
]]>
</screen>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>grapheme_extract</function></member>
<member>
<link xlink:href="&uri.unicode.graphemes;">
Unicode Text Segmentation: Grapheme Cluster Boundaries
</link>
</member>
</simplelist>
</para>
</refsect1>
</refentry>
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