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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<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. A variable is considered empty if it does not exist or if its value equals &false;. <function>empty</function> does not generate a warning if the variable does not exist.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>var</parameter></term>
<listitem>
<para>
Variable to be checked
</para>
<para>
No warning is generated if the variable does not exist.
That means <function>empty</function> is essentially the
concise equivalent to <command>!isset($var) || $var == false</command>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &true; if <parameter>var</parameter> does not exist or has a value that is empty or equal to zero,
aka falsey, see <link linkend="language.types.boolean.casting">conversion to boolean</link>.
Otherwise returns &false;.
</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>
<example>
<title><function>empty</function> on String Offsets</title>
<programlisting role="php">
<![CDATA[
<?php
$expected_array_got_string = 'somestring';
var_dump(empty($expected_array_got_string['some_key']));
var_dump(empty($expected_array_got_string[0]));
var_dump(empty($expected_array_got_string['0']));
var_dump(empty($expected_array_got_string[0.5]));
var_dump(empty($expected_array_got_string['0.5']));
var_dump(empty($expected_array_got_string['0 Mostel']));
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
bool(true)
bool(false)
bool(false)
bool(false)
bool(true)
bool(true)
]]>
</screen>
</example>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
¬e.language-construct;
<note>
<para>
When using <function>empty</function> on inaccessible object properties,
the <link linkend="object.isset">__isset()</link>
overloading method will be called, if declared.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>isset</function></member>
<member><link linkend="object.isset">__isset()</link></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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