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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.13 $ -->
<refentry xml:id="function.empty" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>empty</refname>
<refpurpose>Determine whether a variable is empty</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>bool</type><methodname>empty</methodname>
<methodparam><type>mixed</type><parameter>var</parameter></methodparam>
</methodsynopsis>
<para>
Determine whether a variable is considered to be empty.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>var</parameter></term>
<listitem>
<para>
Variable to be checked
</para>
<note>
<para>
<function>empty</function> only checks variables as anything else will
result in a parse error. In other words, the following will not work:
<command>empty(trim($name))</command>.
</para>
</note>
<para>
<function>empty</function> is the opposite of
<literal>(boolean) var</literal>,
except that no warning is generated when the variable is not set.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &false; if <parameter>var</parameter> has a non-empty
and non-zero value.
</para>
<para>
The following things are considered to be empty:
<simplelist>
<member><literal>"" (an empty string)</literal></member>
<member><literal>0 (0 as an integer)</literal></member>
<member><literal>"0" (0 as a string)</literal></member>
<member>&null;</member>
<member>&false;</member>
<member><literal>array() (an empty array)</literal></member>
<member><literal>var $var; (a variable declared, but without a value in a class)</literal></member>
</simplelist>
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>PHP 5</entry>
<entry>
<para>
As of PHP 5, objects with no properties are no longer considered empty.
</para>
</entry>
</row>
<row>
<entry>PHP 4</entry>
<entry>
<para>
As of PHP 4, The string value "0" is considered empty.
</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title>
A simple <function>empty</function> / <function>isset</function>
comparison.
</title>
<programlisting role="php">
<![CDATA[
<?php
$var = 0;
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
¬e.language-construct;
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>isset</function></member>
<member><function>unset</function></member>
<member><function>array_key_exists</function></member>
<member><function>count</function></member>
<member><function>strlen</function></member>
<member><link linkend="types.comparisons">The type comparison tables</link></member>
</simplelist>
</para>
</refsect1>
</refentry>
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