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<refentry xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://docbook.org/ns/docbook" xml:id="function.strnatcmp">
 <refnamediv>
  <refname>strnatcmp</refname>
  <refpurpose>String comparisons using a "natural order" algorithm</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>strnatcmp</methodname>
   <methodparam><type>string</type><parameter>string1</parameter></methodparam>
   <methodparam><type>string</type><parameter>string2</parameter></methodparam>
  </methodsynopsis>
  <para>
   This function implements a comparison algorithm that orders
   alphanumeric strings in the way a human being would, this is
   described as a "natural ordering".  
   Note that this comparison is case sensitive.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>string1</parameter></term>
     <listitem>
      <para>
       The first string.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>string2</parameter></term>
     <listitem>
      <para>
       The second string.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Similar to other string comparison functions, this one returns <literal>-1</literal> if
   <parameter>string1</parameter> is less than <parameter>string2</parameter>;
   <literal>1</literal> if <parameter>string1</parameter> is greater than
   <parameter>string2</parameter>, and <literal>0</literal> if they are equal.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     &standard.changelog.binary-safe-string-comparison;
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   An example of the difference between this algorithm and the regular
   computer string sorting algorithms (used in <function>strcmp</function>)
   can be seen below:
   <informalexample>
    <programlisting role="php">
<![CDATA[
<?php
$arr1 = $arr2 = array("img12.png", "img10.png", "img2.png", "img1.png");
echo "Standard string comparison\n";
usort($arr1, "strcmp");
print_r($arr1);
echo "\nNatural order string comparison\n";
usort($arr2, "strnatcmp");
print_r($arr2);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Standard string comparison
Array
(
    [0] => img1.png
    [1] => img10.png
    [2] => img12.png
    [3] => img2.png
)

Natural order string comparison
Array
(
    [0] => img1.png
    [1] => img2.png
    [2] => img10.png
    [3] => img12.png
)
]]>
    </screen>
   </informalexample>
   For more information see: Martin Pool's <link
   xlink:href="&url.strnatcmp;">Natural Order String Comparison</link>
   page.
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>preg_match</function></member>
    <member><function>strcasecmp</function></member>
    <member><function>substr</function></member>
    <member><function>stristr</function></member>
    <member><function>strcmp</function></member>
    <member><function>strncmp</function></member>
    <member><function>strncasecmp</function></member>
    <member><function>strnatcasecmp</function></member>
    <member><function>strstr</function></member>
    <member><function>natsort</function></member>
    <member><function>natcasesort</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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