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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://docbook.org/ns/docbook" xml:id="function.chr">
<refnamediv>
<refname>chr</refname>
<refpurpose>Generate a single-byte string from a number</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>string</type><methodname>chr</methodname>
<methodparam><type>int</type><parameter>codepoint</parameter></methodparam>
</methodsynopsis>
<para>
Returns a one-character string containing the character specified
by interpreting <parameter>codepoint</parameter> as an unsigned integer.
</para>
<para>
This can be used to create a one-character string in a single-byte encoding such as ASCII, ISO-8859, or Windows 1252, by passing the position of a desired character in the encoding's mapping table. However, note that this function is not aware of any string encoding, and in particular cannot be passed a Unicode code point value to generate a string in a multibyte encoding like UTF-8 or UTF-16.
</para>
<para>
This function complements <function>ord</function>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>codepoint</parameter></term>
<listitem>
<para>
An integer between 0 and 255.
</para>
<para>
Values outside the valid range (0..255) will be bitwise and'ed with 255,
which is equivalent to the following algorithm:
<programlisting role="php">
<![CDATA[
while ($bytevalue < 0) {
$bytevalue += 256;
}
$bytevalue %= 256;
]]>
</programlisting>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
A single-character string containing the specified byte.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>7.4.0</entry>
<entry>
The function no longer silently accepts unsupported <parameter>codepoint</parameter>s,
and casts these to <literal>0</literal>.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>chr</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// Assumes the string will be used as ASCII or an ASCII-compatible encoding
$str = "The string ends in escape: ";
$str .= chr(27); /* add an escape character at the end of $str */
/* Often this is more useful */
$str = sprintf("The string ends in escape: %c", 27);
?>
]]>
</programlisting>
</example>
<example>
<title>Overflow behavior</title>
<programlisting role="php">
<![CDATA[
<?php
echo chr(-159), chr(833), PHP_EOL;
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
aA
]]>
</screen>
</example>
</para>
<para>
<example>
<title>Building a UTF-8 string from individual bytes</title>
<programlisting role="php">
<![CDATA[
<?php
$str = chr(240) . chr(159) . chr(144) . chr(152);
echo $str;
?>
]]>
</programlisting>
&example.outputs;
<screen>
🐘
</screen>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>sprintf</function> with a format string of <literal>%c</literal></member>
<member><function>ord</function></member>
<member>An <link xlink:href="&url.asciitable;">ASCII-table</link></member>
<member><function>mb_chr</function></member>
<member><function>IntlChar::chr</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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sgml-minimize-attributes:nil
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|
