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>
     </methodsynopsis>
    <para>
     Returns the number of elements in <parameter>var</parameter>,
     which is typically an <type>array</type> (since anything else will have
     one element).
    </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>
    <warning>
     <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>
    </warning>
    <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>
    <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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