php-doc-en/reference/math/functions/rand.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.rand" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>rand</refname>
  <refpurpose>Generate a random integer</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>rand</methodname>
   <void/>
  </methodsynopsis>
  <methodsynopsis>
   <type>int</type><methodname>rand</methodname>
   <methodparam><type>int</type><parameter>min</parameter></methodparam>
   <methodparam><type>int</type><parameter>max</parameter></methodparam>
  </methodsynopsis>
  <simpara>
   If called without the optional <parameter>min</parameter>,
   <parameter>max</parameter> arguments <function>rand</function>
   returns a pseudo-random integer between 0 and
   <function>getrandmax</function>.  If you want a random number
   between 5 and 15 (inclusive), for example, use <literal>rand(5,
   15)</literal>.
  </simpara>
  &caution.cryptographically-insecure;
  <note>
   <simpara>
    On some platforms (such as Windows), <function>getrandmax</function>
    is only 32767.  If you require a range larger than 32767, specifying
    <parameter>min</parameter> and <parameter>max</parameter> will allow
    you to create a range larger than this, or consider using
    <function>mt_rand</function> instead.
   </simpara>
  </note>
  <note><simpara>As of PHP 7.1.0, <function>rand</function> uses the same
   random number generator as <function>mt_rand</function>. To preserve
   backwards compatibility <function>rand</function> allows
   <parameter>max</parameter> to be smaller than <parameter>min</parameter>
   as opposed to returning &false; as <function>mt_rand</function>.</simpara>
  </note>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>min</parameter></term>
     <listitem>
      <para>
       The lowest value to return (default: 0)
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>max</parameter></term>
     <listitem>
      <para>
       The highest value to return (default: <function>getrandmax</function>)
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   A pseudo random value between <parameter>min</parameter>
   (or 0) and <parameter>max</parameter> (or <function>getrandmax</function>, inclusive).
  </para>
 </refsect1>
 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>7.2.0</entry>
       <entry>
        <function>rand</function> <link linkend="migration72.incompatible.rand-mt_rand-output">has received a bug fix</link> for a modulo bias bug. This means that sequences generated with a specific seed may differ from PHP 7.1 on 64-bit machines.
       </entry>
      </row>
      <row>
       <entry>7.1.0</entry>
       <entry>
        <function>rand</function> <link linkend="migration71.incompatible.rand-srand-aliases">has been made</link> an alias of <function>mt_rand</function>.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>rand</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
echo rand() . "\n";
echo rand() . "\n";

echo rand(5, 15);
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
7771
22264
11
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 
 <refsect1 role="notes">
  &reftitle.notes;
  <warning>
   <para>
    <parameter>min</parameter> <parameter>max</parameter> range must
    be within the range <function>getrandmax</function>. i.e. (<parameter>max</parameter> -
    <parameter>min</parameter>) &lt;= <function>getrandmax</function>
    Otherwise, <function>rand</function> may return poor-quality random numbers.
   </para>
  </warning>
 </refsect1>
 
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>srand</function></member>
    <member><function>getrandmax</function></member>
    <member><function>mt_rand</function></member>
    <member><function>random_int</function></member>
    <member><function>random_bytes</function></member>
    <member><function>openssl_random_pseudo_bytes</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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