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

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.count" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>count</refname>
  <refpurpose>Count all elements in an array, or something in an object</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>count</methodname>
   <methodparam><type>mixed</type><parameter>array_or_countable</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>mode</parameter><initializer>COUNT_NORMAL</initializer></methodparam>
  </methodsynopsis>
  <para>
   Counts all elements in an array, or something in an object.
  </para>
  <para>
   For objects, if you have
   <link linkend="ref.spl">SPL</link> installed, you can hook into
   <function>count</function> by implementing interface
   <classname>Countable</classname>. The interface has exactly one method,
   <methodname>Countable::count</methodname>, which returns the return value for the
   <function>count</function> function.
  </para>
  <para>
   Please see the <link linkend="language.types.array">Array</link>
   section of the manual for a detailed explanation of how arrays
   are implemented and used in PHP.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>array_or_countable</parameter></term>
     <listitem>
      <para>
       An array or <classname>Countable</classname> object.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>mode</parameter></term>
     <listitem>
      <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.
      </para>
      <caution>
       <para>
        <function>count</function> can detect recursion to avoid an infinite
        loop, but will emit an <constant>E_WARNING</constant> every time it
        does (in case the array contains itself more than once) and return a
        count higher than may be expected.
       </para>
      </caution>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the number of elements in <parameter>array_or_countable</parameter>.
   When the parameter is neither an array nor an object with
   implemented <classname>Countable</classname> interface,
   <literal>1</literal> will be returned.
   There is one exception, if <parameter>array_or_countable</parameter> is &null;,
   <literal>0</literal> will be returned.
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>count</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
var_dump(count($a));

$b[0]  = 7;
$b[5]  = 9;
$b[10] = 11;
var_dump(count($b));

var_dump(count(null));

var_dump(count(false));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
int(3)
int(3)

Warning: count(): Parameter must be an array or an object that implements Countable in … on line 12 // as of PHP 7.2
int(0)

Warning: count(): Parameter must be an array or an object that implements Countable in … on line 14 // as of PHP 7.2
int(1)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title>Recursive <function>count</function> example</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>
 </refsect1>
 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>7.2.0</entry>
      <entry>
       <function>count</function> will now yield a warning on invalid countable types 
       passed to the <parameter>array_or_countable</parameter> parameter.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>is_array</function></member>
    <member><function>isset</function></member>
    <member><function>empty</function></member>
    <member><function>strlen</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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