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

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  <refentry id="function.count">
   <refnamediv>
    <refname>count</refname>
    <refpurpose>Count elements in a variable</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>count</methodname>
      <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>mode</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns the number of elements in <parameter>var</parameter>,
     which is typically an <type>array</type> (since anything other than objects 
     will have one element).
    </para>
    <para>
     For objects it returns the number of non static properties not taking
     visibility into account. If you have SPL starting from PHP 5.1 you can 
     hook into coun() by implementing interface Countable. That interface
     has exactly one method named count() which delivers the return value
     for the count() function.
    </para>
    <para>
     If <parameter>var</parameter> is not an array, <literal>1</literal> will
     be returned (exception: <literal>count(&null;)</literal> equals
     <literal>0</literal>).
    </para>
    <note>
     <simpara>
      The optional <parameter>mode</parameter> parameter is available as of 
      PHP 4.2.0.
     </simpara>
    </note>
    <para>
     If the optional <parameter>mode</parameter> parameter is set to 
     <constant>COUNT_RECURSIVE</constant> (or 1), <function>count</function> 
     will recursively count the array.  This is particularly useful for 
     counting all the elements of a multidimensional array.  The default
     value for <parameter>mode</parameter> is <literal>0</literal>.
     <function>count</function> does not detect infinite recursion.
    </para>
    <caution>
     <para>
      <function>count</function> may return 0 for a variable that
      isn't set, but it may also return 0 for a variable that has
      been initialized with an empty array. Use
      <function>isset</function> to test if a variable is set.
     </para>
    </caution>
    <para>
     Please see the <link linkend="language.types.array">Arrays</link>
     section of the manual for a detailed explanation of how arrays
     are implemented and used in PHP.
    </para>
    <para>
     <example>
      <title><function>count</function> example</title>
      <programlisting role="php">
      <!-- TODO: examples about count(null), count(false), count(object).. -->
<![CDATA[
<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
$result = count($a);
// $result == 3

$b[0]  = 7;
$b[5]  = 9;
$b[10] = 11;
$result = count($b);
// $result == 3;
?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <example>
      <title>
       recursive <function>count</function> example (PHP &gt;= 4.2.0)
      </title>
      <programlisting role="php">
<![CDATA[
<?php
$food = array('fruits' => array('orange', 'banana', 'apple'),
              'veggie' => array('carrot', 'collard', 'pea'));

// recursive count
echo count($food, COUNT_RECURSIVE);  // output 8

// normal count
echo count($food);                  // output 2

?>
]]>
      </programlisting>
     </example>
    </para>
    <note>
     <para>
      The <function>sizeof</function> function is an
      <link linkend="aliases">alias</link> for <function>count</function>.
     </para>
    </note>
    <para>
     See also <function>is_array</function>,
     <function>isset</function>, and
     <function>strlen</function>.
    </para>
   </refsect1>
  </refentry>

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