archived-doc-en/reference/random/functions/random-bytes.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.random-bytes" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>random_bytes</refname>
  <refpurpose>Get cryptographically secure random bytes</refpurpose>
 </refnamediv>

 <refsect1 role="description"><!-- {{{ -->
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>random_bytes</methodname>
   <methodparam><type>int</type><parameter>length</parameter></methodparam>
  </methodsynopsis>
  <para>
   Generates a string containing uniformly selected random bytes with the requested <parameter>length</parameter>.
  </para>
  <para>
   As the returned bytes are selected completely randomly, the resulting string is likely
   to contain unprintable characters or invalid UTF-8 sequences. It may be necessary to
   encode it before transmission or display.
  </para>
  <para>
   The randomness generated by this function is suitable for all applications, including
   the generation of long-term secrets, such as encryption keys.
  </para>
  &csprng.sources;
  &csprng.function.backport;
 </refsect1><!-- }}} -->

 <refsect1 role="parameters"><!-- {{{ -->
  &reftitle.parameters;
  <variablelist>
   <varlistentry>
    <term><parameter>length</parameter></term>
    <listitem>
     <para>
      The length of the random string that should be returned in bytes; must be <literal>1</literal> or greater.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1><!-- }}} -->

 <refsect1 role="returnvalues"><!-- {{{ -->
  &reftitle.returnvalues;
  <para>
   A string containing the requested number of cryptographically
   secure random bytes.
  </para>
 </refsect1><!-- }}} -->

 <refsect1 role="errors"><!-- {{{ -->
  &reftitle.errors;
  <itemizedlist>
   &csprng.errors;
   <listitem>
    <simpara>
     If the value of <parameter>length</parameter> is less than <literal>1</literal>,
     a <classname>ValueError</classname> will be thrown.
    </simpara>
   </listitem>
  </itemizedlist>
 </refsect1><!-- }}} -->

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.2.0</entry>
      <entry>
       In case of a <acronym>CSPRNG</acronym> failure, this function will now throw a
       <classname>Random\RandomException</classname>. Previously a plain
       <classname>Exception</classname> was thrown.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples"><!-- {{{ -->
  &reftitle.examples;
  <example xml:id="random-bytes.example.basic"><!-- {{{ -->
   <title><function>random_bytes</function> example</title>
   <programlisting role="php">
<![CDATA[
<?php
$bytes = random_bytes(5);
var_dump(bin2hex($bytes));
?>
]]>
   </programlisting>
   &example.outputs.similar;
   <screen>
<![CDATA[
string(10) "385e33f741"
]]>
   </screen>
  </example><!-- }}} -->
 </refsect1><!-- }}} -->

 <refsect1 role="seealso"><!-- {{{ -->
  &reftitle.seealso;
  <simplelist>
   <member><function>Random\Randomizer::getBytes</function></member>
   <member><function>random_int</function></member>
   <member><function>bin2hex</function></member>
   <member><function>base64_encode</function></member>
  </simplelist>
 </refsect1><!-- }}} -->

</refentry>
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