php-doc-en/reference/array/functions/array-unique.xml

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<refentry xml:id="function.array-unique" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>array_unique</refname>
  <refpurpose>Removes duplicate values from an array</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>array_unique</methodname>
   <methodparam><type>array</type><parameter>array</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter><initializer>SORT_STRING</initializer></methodparam>
  </methodsynopsis>
  <para>
   Takes an input <parameter>array</parameter> and returns a new array
   without duplicate values.
  </para>
  <para>
   Note that keys are preserved. <function>array_unique</function> sorts
   the values treated as string at first, then will keep the first key
   encountered for every value, and ignore all following keys. It does not
   mean that the key of the first related value from the unsorted
   <parameter>array</parameter> will be kept.
  </para>
  <note>
   <simpara>
    Two elements are considered equal if and only if
    <literal>(string) $elem1 === (string) $elem2</literal> i.e. 
    when the string representation is the same, the first element will be used.
   </simpara>
  </note>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>array</parameter></term>
     <listitem>
      <para>
       The input array.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>sort_flags</parameter></term>
     <listitem>
      <para>
       The optional second parameter <parameter>sort_flags</parameter>
       may be used to modify the sorting behavior using these values:
      </para>
      <para>
       Sorting type flags:
       <itemizedlist>
        <listitem>
         <simpara><constant>SORT_REGULAR</constant> - compare items normally
         (don't change types)</simpara>
        </listitem>
        <listitem>
         <simpara><constant>SORT_NUMERIC</constant> - compare items numerically</simpara>
        </listitem>
        <listitem>
         <simpara><constant>SORT_STRING</constant> - compare items as strings</simpara>
        </listitem>
        <listitem>
         <simpara><constant>SORT_LOCALE_STRING</constant> - compare items as
          strings, based on the current locale.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the filtered array.
  </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>5.2.10</entry>
       <entry>
        Changed the default value of <parameter>sort_flags</parameter> back to
        <constant>SORT_STRING</constant>.
       </entry>
      </row>
      <row>
       <entry>5.2.9</entry>
       <entry>
        Added the optional <parameter>sort_flags</parameter> defaulting
        to <constant>SORT_REGULAR</constant>. Prior to 5.2.9, this function used to sort
        the array with <constant>SORT_STRING</constant> internally.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_unique</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
Array
(
    [a] => green
    [0] => red
    [1] => blue
)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><function>array_unique</function> and types</title>
    <programlisting role="php">
<![CDATA[
<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_count_values</function></member>
   </simplelist>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <simpara>
    Note that <function>array_unique</function> is not intended to 
    work on multi dimensional arrays.
   </simpara>
  </note>
 </refsect1>

</refentry>

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