archived-doc-en/reference/array/functions/array-rand.xml

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<refentry xml:id="function.array-rand" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>array_rand</refname>
  <refpurpose>Pick one or more random keys out of an array</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>int</type><type>string</type><type>array</type></type><methodname>array_rand</methodname>
   <methodparam><type>array</type><parameter>array</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>num</parameter><initializer>1</initializer></methodparam>
  </methodsynopsis>
  <para>
   Picks one or more random entries out of an array, and returns the
   key (or keys) of the random entries.
  </para>
  &caution.cryptographically-insecure;
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>array</parameter></term>
     <listitem>
      <para>
       The input array.
       Cannot be empty.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>num</parameter></term>
     <listitem>
      <para>
       Specifies how many entries should be picked.
       Must be greater than zero, and less than or equal to the length of <parameter>array</parameter>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   When picking only one entry, <function>array_rand</function> returns
   the key for a random entry. Otherwise, an array of keys for the random
   entries is returned. This is done so that random keys can be picked
   from the array as well as random values. If multiple keys are returned,
   they will be returned in the order they were present in the original array.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   Throws a <classname>ValueError</classname> if <parameter>array</parameter> is empty,
   or if <parameter>num</parameter> is out of range.
  </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>8.0.0</entry>
       <entry>
        <function>array_rand</function> now throws a <classname>ValueError</classname>
        if <parameter>num</parameter> is out of range; previously an
        <constant>E_WARNING</constant> was raised, and the function returned &null;.
       </entry>
      </row>
      <row>
       <entry>8.0.0</entry>
       <entry>
        <function>array_rand</function> now throws a <classname>ValueError</classname>
        if <parameter>array</parameter> is empty; previously an
        <constant>E_WARNING</constant> was raised, and the function returned &null;.
       </entry>
      </row>
      <row>
       <entry>7.1.0</entry>
       <entry>
        The internal randomization algorithm <link linkend="migration71.incompatible.rand-srand-aliases">has been changed</link> to use the <link xlink:href="&url.mersenne;">Mersenne Twister</link> Random Number Generator instead of the libc rand function.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_rand</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$rand_keys = array_rand($input, 2);
echo $input[$rand_keys[0]] . "\n";
echo $input[$rand_keys[1]] . "\n";
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>Random\Randomizer::pickArrayKeys</function></member>
    <member><function>Random\Randomizer::shuffleArray</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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