array-slice.xml

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<refentry xml:id="function.array-slice" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>array_slice</refname>
  <refpurpose>Extract a slice of the array</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>array_slice</methodname>
   <methodparam><type>array</type><parameter>array</parameter></methodparam>
   <methodparam><type>int</type><parameter>offset</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>length</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>preserve_keys</parameter><initializer>&false;</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>array_slice</function> returns the sequence of elements
   from the array <parameter>array</parameter> as specified by the
   <parameter>offset</parameter> and <parameter>length</parameter>
   parameters.
  </para>
 </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>offset</parameter></term>
     <listitem>
      <para>
       If <parameter>offset</parameter> is non-negative, the sequence will
       start at that offset in the <parameter>array</parameter>.
      </para>
      <para>
       If <parameter>offset</parameter> is negative, the sequence will
       start that far from the end of the <parameter>array</parameter>.
      </para>
      <note>
       <para>
        The <parameter>offset</parameter> parameter denotes the position
        in the array, not the key.
       </para>
      </note>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>length</parameter></term>
     <listitem>
      <para>
       If <parameter>length</parameter> is given and is positive,
       then the sequence will have up to that many elements in it.
      </para>
      <para>
       If the array is shorter than the <parameter>length</parameter>,
       then only the available array elements will be present.
      </para>
      <para>
       If <parameter>length</parameter> is given and is negative then the
       sequence will stop that many elements from the end of the array.
      </para>
      <para>
       If it is omitted, then the sequence will have everything
       from <parameter>offset</parameter> up until the end of the
       <parameter>array</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>preserve_keys</parameter></term>
     <listitem>
      <note>
       <para>
        <function>array_slice</function> will reorder and reset the
        integer array indices by default. This behaviour can be changed
        by setting <parameter>preserve_keys</parameter> to &true;.
        String keys are always preserved, regardless of this parameter.
       </para>
      </note>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the slice. If the offset is larger than the size of the array,
   an empty array is returned.
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_slice</function> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
$input = array("a", "b", "c", "d", "e");

$output = array_slice($input, 2);      // returns "c", "d", and "e"
$output = array_slice($input, -2, 1);  // returns "d"
$output = array_slice($input, 0, 3);   // returns "a", "b", and "c"

// note the differences in the array keys
print_r(array_slice($input, 2, -1));
print_r(array_slice($input, 2, -1, true));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Array
(
    [0] => c
    [1] => d
)
Array
(
    [2] => c
    [3] => d
)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><function>array_slice</function> and one-based array</title>
    <programlisting role="php">
<![CDATA[
<?php
$input = array(1 => "a", "b", "c", "d", "e");
print_r(array_slice($input, 1, 2));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Array
(
    [0] => b
    [1] => c
)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><function>array_slice</function> and array with mixed keys</title>
    <programlisting role="php">
<![CDATA[
<?php
$ar = array('a'=>'apple', 'b'=>'banana', '42'=>'pear', 'd'=>'orange');
print_r(array_slice($ar, 0, 3));
print_r(array_slice($ar, 0, 3, true));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Array
(
    [a] => apple
    [b] => banana
    [0] => pear
)
Array
(
    [a] => apple
    [b] => banana
    [42] => pear
)
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_chunk</function></member>
    <member><function>array_splice</function></member>
    <member><function>unset</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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